:orphan: µGFX Guide ========== :link_to_translation:`zh_CN:[中文]` Introduction ------------ 1. What is µGFX? `μGFX `__ is a lightweight embedded library for displays and touchscreens, providing everything required to build a fully featured embedded GUI. The library is very small and fast, because every unused feature is disabled and not linked into the finished binary. µGFX features at a glance - Lightweight - Modular - Portable - Open-source 100% - Actively Developed 2. µGFX is a complete solution. The µGFX library has been designed to be the smallest, fastest and most advanced embedded library for display and touchscreen solutions. µGFX features - Small and lightweight - Fully customizable and extendable - Highly portable - Support for all display types: Monochrome, grayscale, and full color displays - Support for hardware acceleration - Over 50 ready-to-use drivers - Written in C and can be used with C++ - Free for non-commercial uses - Fully Transparent: The entire source-code is open - Works on low RAM systems. A frame buffer is not required for most displays - Fully multi-threading re-entrant. Drawing can occur from any thread, at any time! 3. Desktop GUI Designer The μGFX-Studio is a desktop application that provides a drag'n'drop interface to quickly assemble a graphical user interface. It runs on Windows, Linux and Mac OS X. The μGFX-Studio is not fully accessible at the moment. µGFX modules ~~~~~~~~~~~~ The µGFX library has the following modules: - `GWIN <#gwin>`__ - The GWIN module uses all the other modules and combines them into a complete GUI toolkit. It provides everything from buttons, checkboxes, lists to graph widgets and much more. - GAUDIO - The GAUDIO module provides high level API for handling audio input and output. The module features built-in decoders but also allows to use external codecs. - GFILE - The GFILE module provides an operating-system-independent way of reading and writing files, no matter whether they are stored in RAM, FLASH, an SD Card or a native file system in host operating systems. - GOS - GOS is the module which builds the abstraction layer between µGFX and the underlying system. The underlying system can be an RTOS, such as ChibiOS or FreeRTOS, or just a bare metal system. - `GDISP <#gdisp>`__ - The GDISP module provides a simple interface for graphic displays and a feature-rich set of APIs to draw primitive shapes such as lines, circles and rectangles, as well as font rendering, clipping and other advanced features. - GINPUT - GINPUT is a powerful module which provides an easy way to interface different hardware peripherals, such as touchscreens, to the rest of the library. It provides calibration routines for the touchscreens. - GTRANS - The GTRANS module allows you to manage language translations. The language of an application can be changed dynamically during run-time using the GTRANS module. - GEVENT - The GEVENT module is a very powerful event system. It provides a way to create a many-to-many relationships between sources and listeners. - GTIMER - The GTIMER module provides high-level, simple and hardware independent timers. - GQUEUE - The GQUEUE module provides implementations of different queues and buffers. GWIN ^^^^ The GWIN module contains: - `Windows <#windows>`__ - Console - Graph window - `Widgets <#widgets>`__ - Label - PushButton - RadioButton - CheckBox - List - Slider - Progressbar - ImageBox - TextEdit - Keyboard - `Containers <#containers>`__ - Container - Tabset - Frame GDISP ^^^^^ The GDISP module contains: - Drawing - Font rendering - Images License ~~~~~~~ Espressif has been granted the µGFX license, so all the Espressif chip users may use the drivers and services provided by µGFX free of charge. About µGFX License, please refer to `License `__. Get started with µGFX --------------------- The Espressif's iot-solution offers drivers adapted to µGFX. You can find them by going to `esp-iot-solution `__. The drivers are stored at the following path: ``components/hmi/gdrivers``. Below is a step-by-step guide on how to use µGFX for the projects based on iot-solution: 1. Build the iot-solution environment: `Preparation `__. 2. Add the header file ``#include "iot_ugfx.h"`` to the project source code. 3. Enable µGFX GUI with ``menuconfig`` (``IoT Solution settings > IoT Components Management > HMI components > uGFX GUI Enable``). 4. `Configure <#configure-µgfx>`__ µGFX GUI with ``menuconfig`` (``IoT Solution settings > IoT Components Management > HMI components > uGFX Settings``). 5. Initialize µGFX according to the example project ``ugfx_example``. 6. Develop GUI according to your actual requirements. µGFX related `API Reference `__ Configure µGFX ~~~~~~~~~~~~~~ There are two ways to configure µGFX in iot-solution: 1. Configure µGFX with ``menuconfig`` To simplify the configuration process, you can add the frequently used configurations, such as a driver configuration, touchscreen enabling, screen resolution and orientation, to ``menuconfig``. The path to the µGFX configuration menu is ``IoT Solution settings > IoT Components Management > HMI components > uGFX Settings``. 2. Configure µGFX by modifying the file ``gfxconf.h`` All project-specific options for µGFX are defined in the file ``gfxconf.h``, which can be found at the path ``esp-iot-solution/components/hmi/gdrivers/include/gfxconf.h``. You can modify the file according to your requirements. Within each section, the very first option enables or disables the entire module. All the following sub-options only take effect when the module is enabled. For the detailed information about the file ``gfxconf.h``, please refer to `Configuration `__. The figure below shows the µGFX configuration options in ``menuconfig``. .. figure:: ../../_static/hmi_solution/ugfx/ugfx_menuconfig.jpg :align: center 1. Configure drivers In the µGFX Settings menu, you can configure the drivers for displays and touchscreens. To do this, please go to ``Config Driver->Choose Touch Screen Driver`` and ``Config Driver->Choose Screen Driver``. 2. Enable touchscreens The µGFX Settings menu allows you to enable or disable the touchscreen. To do this, please go to ``uGFX Touch Screen Enable``. 3. Configure screen resolution To configure the screen resolution in the µGFX Settings menu, please go to ``Config Driver->uGFX Screen Width (pixels)`` and ``Config Driver->uGFX Screen Height (pixels)``. 4. Configure screen orientation To configure the screen orientation in the µGFX Settings menu, please go to ``Choose Screen Rotate``. Display driver model ~~~~~~~~~~~~~~~~~~~~ A µGFX display driver supports three models. Unlike desktop graphics processors, embedded LCDs often have a very different access model, which means the traditional graphics libraries do not support them efficiently, if at all. Some graphics controllers may require different models in different situations. 1. Framebuffer model This is the model that most graphics libraries support and is most suitable for advanced graphics processors. It requires that the graphics hardware supplies a framebuffer which is a block of RAM that is pixel addressable as normal memory from the CPU side. The graphics hardware then updates the display in the background by seeing the changes that the CPU makes to the framebuffer. It is also the simplest type of new hardware to support in µGFX. Many other graphics libraries try to support other types of hardware by allocating system RAM to a virtual framebuffer and then providing a sync call to flush the framebuffer to the real display. This has a number of issues, such as: - It allocates large amounts of system RAM which is often a precious resource in an embedded environment. - The sync call is usually very inefficient as either the entire display must be updated or a difference comparison must be made. There may be other reasons that a sync is needed (e.g. to allow updating of the display only during vertical refresh), so µGFX still supports a sync call. It is strongly recommended not to use this model, unless your graphics hardware supports a native framebuffer. Required functions: - ``board_init()``: Initialize the framebuffer and return its address and the display properties Optional functions: - ``board_flush()``: Flush (sync) the framebuffer to the display - ``board_backlight()``: Adjust the display backlight - ``board_contrast()``: Adjust the display contrast - ``board_power()``: Enter/Exit sleep modes 2. Window model Most embedded LCDs use this model of controller. Unfortunately most graphics libraries do not support these controllers efficiently. In this model, the hardware provides a programmable window area. This window area is written to by sequentially sending pixels to the graphics controller. When the pixels reach the end of a line in the window, the controller wraps to the start of the next line in the window. When it reaches the bottom of the window, it may (or may not) wrap back to the beginning of the window. Reading from the display is often not supported, and if it is, this is done with the same windowed method. As the display surface is not RAM addressable and the physical connections are often via a slow bus (at least compared to RAM addressing) such as SPI, I2C or byte parallel, the reading and writing speed can be slow. This means that efficiency of the drawing operations is very important and completely different methods of drawing need to be used compared to a framebuffer. µGFX automatically handles all of these differences. Screen rotation only for software is not possible with these controllers (unlike a framebuffer). Some hardware support is required. However, there are two possible ways to achieve this: (1) by rotating the way the cursor is moved within the drawing window, or (2) by rotating the display itself relative to the internal framebuffer. By policy, the priority is that the first method be implemented if the controller supports both. This preference allows retention of existing display contents with the rotation only affecting new drawing operations (more flexible for the end-user application). Required functions: - ``gdisp_lld_init()``: Initialize the controller and display - ``gdisp_lld_write_start()``: Start a windowed write operation - ``gdisp_lld_write_color()``: Send one pixel to the current window at the current position - ``gdisp_lld_write_stop()``: Stop a windowed write operation Optional functions: - ``gdisp_lld_write_pos()``: Set the current position within the write window (increases drawing efficiency) - ``gdisp_lld_read_start()``: Start a windowed read operation - ``gdisp_lld_read_color()``: Read one pixel from the current window at the current position - ``gdisp_lld_read_stop()``: Stop a windowed read operation - ``gdisp_lld_set_clip()``: Set a hardware clipping region. All writes are clipped to this area (regardless of the current window) - ``gdisp_lld_control()``: Handle backlight, contrast, screen orientation and any driver specific control commands - ``gdisp_lld_query()``: Query some driver specific values - Any Point and Block model functions as described below 3. Point and Block model In this model, the controller provides basic drawing operations such as set-point, fill-block, fill-block-from-image. Many of the window model principles apply here. Reading from the display is often not supported. Drivers may mix the functions from this model into the window model above. If a specific set-point, fill-block or fill-block-from-image function is provided in a window model driver, it will have a higher priority over the general window model calls above. When calls are mixed like this, the driver is still considered to be a window model driver. For example, a controller may have a more efficient set-point command that can be prioritized over a windowed single pixel write. Required functions: - ``gdisp_lld_init()``: Initialize the controller and display - ``gdisp_lld_draw_pixel()``: Set a single pixel Optional functions: - ``gdisp_lld_fill_area()``: Fill a block with a color - ``gdisp_lld_blit_area()``: Fill a block from an array of pixels - ``gdisp_lld_vertical_scroll()``: Scroll up or down a windowed area of the display - ``gdisp_lld_get_pixel_color()``: Get the color of a single pixel - ``gdisp_lld_set_clip()``: Set a hardware clipping region. All writes are clipped to this area. - ``gdisp_lld_control()``: Handle backlight, contrast, screen orientation, and any driver specific control commands - ``gdisp_lld_query()``: Query some driver specific values Set fonts ~~~~~~~~~ 1. Usage To make a font available, open it by calling the function ``gdispOpenFont()``. For example: ``font_t font = gdispOpenFont("DejaVuSans32_aa");`` If the specified font name cannot be found, the last enabled font in the configuration file will be used. To open the first enabled font please use ``gdispOpenFont("*");``. After a font is opened, its variable can be passed to any API with a font parameter. You can start by reading through the basic GDISP text drawing functions before you take a look at the different GWIN system. If a font is no longer needed, call the function ``gdispCloseFont(font)`` to release the allocated resources. 2. Set default fonts Call the function ``gwinSetDefaultFont(font_t font)`` to set the default fonts for all GUI elements. For example: :: #include "iot_ugfx.h" static font_t font; int main(void) { // Initialize uGFX and the underlying system gfxInit(); // Set the widget defaults font = gdispOpenFont("DejaVuSans16"); gwinSetDefaultFont(font); } 3. Set the font for a GUI element To set a font for a GUI element, call the function ``gwinSetFont(GHandle gh, font_t font)``. 4. µGFX available fonts Every font that is available in a .ttf or .bdf format can be displayed through µGFX. However, µGFX comes with a bunch of fonts in different sizes and versions which should cover most use cases. Use the font name (see the table below) as the parameter of the function ``gdispOpenFont()``. Note that each of these fonts has to be enabled in your configuration file. The UI fonts are default fonts created by µGFX developers. +------------------------------------+------------------------+ | **Font** | **Font name** | +====================================+========================+ | DejaVu Sans 10 | DejaVuSans10 | +------------------------------------+------------------------+ | DejaVu Sans 12 | DejaVuSans12 | +------------------------------------+------------------------+ | DejaVu Sans 12 Bold | DejaVuSansBold12 | +------------------------------------+------------------------+ | DejaVu Sans 12 Anti-Aliased | DejaVuSans12\_aa | +------------------------------------+------------------------+ | DejaVu Sans 12 Anti-Aliased Bold | DejaVuSansBold12\_aa | +------------------------------------+------------------------+ | DejaVu Sans 16 | DejaVuSans16 | +------------------------------------+------------------------+ | DejaVu Sans 16 Anti-Aliased | DejaVuSans16\_aa | +------------------------------------+------------------------+ | DejaVu Sans 20 | DejaVuSans20 | +------------------------------------+------------------------+ | DejaVu Sans 20 Anti-Aliased | DejaVuSans20\_aa | +------------------------------------+------------------------+ | DejaVu Sans 24 | DejaVuSans24 | +------------------------------------+------------------------+ | DejaVu Sans 24 Anti-Aliased | DejaVuSans24\_aa | +------------------------------------+------------------------+ | DejaVu Sans 32 | DejaVuSans32 | +------------------------------------+------------------------+ | DejaVu Sans 32 Anti-Aliased | DejaVuSans32\_aa | +------------------------------------+------------------------+ | Fixed 10x20 | fixed\_10x20 | +------------------------------------+------------------------+ | Fixed 7x14 | fixed\_7x14 | +------------------------------------+------------------------+ | Fixed 5x8 | fixed\_5x8 | +------------------------------------+------------------------+ | UI1 | UI1 | +------------------------------------+------------------------+ | UI1 Double | UI1 Double | +------------------------------------+------------------------+ | UI1 Narrow | UI1 Narrow | +------------------------------------+------------------------+ | UI2 | UI2 | +------------------------------------+------------------------+ | UI2 Double | UI2 Double | +------------------------------------+------------------------+ | UI2 Narrow | UI2 Narrow | +------------------------------------+------------------------+ | Large numbers | LargeNumbers | +------------------------------------+------------------------+ Display images ~~~~~~~~~~~~~~ RAM usage ^^^^^^^^^ The GDISP module comes with a built-in image decoder to open and display images in various formats. As the GFILE module is used internally, images can be read from any location, be it the internal flash or external memory (e.g. SD card). Image decoders use RAM to decode and display images. Although, image handlers are written from scratch to use as little RAM as possible, the image formats used with small microcontrollers should be chosen carefully, because of limited RAM. Image handlers, as most of other image decoders, do not allocate RAM to store a full decompressed bitmap, instead the image is decoded again if it needs to be displayed. RAM is only allocated for the following purposes: - **Storing information about an opened image.** The memory size is typically 200 to 300 bytes and may vary slightly for some images and image formats (e.g. with palettes). This RAM remains occupied while the image is open. - **Decoding an image.** This RAM gets released as soon as the decoding is finished. Decoding GIF images requires around 12 KB of RAM. Decoding BMP and NATIVE images does not require any extra RAM. - **Caching a chosen image.** In this case, RAM is required for the full decoded image. This is not an option for low-memory microprocessors. For example, caching a 320x240 image on a 2 bytes per pixel display takes 150 KB of RAM, plus the RAM for decoding. - **Stack space.** If you get exceptions when trying to decode images, consider increasing the available stack space. Some image formats require a few hundred bytes of stack space to decode an image. µGFX image decoders have been written from scratch to keep the image decoders as lean and mean as possible. These decoders use significantly less RAM than other decoding libraries available. Caching ^^^^^^^ You can choose to cache a decoded image into your RAM by calling the function ``gdispImageCache()``. If an image is not cached, opening it repeatedly will require re-reading from flash, re-decoding, and only then displaying. However, a cached image, only needs to be loaded from RAM and displayed. If an image is cached, you just need to load it from RAM and display it. Caching helps display images much faster, especially the formats with complicated decoding algorithms, such as PNG, JPG, or GIF. Although, caching large-sized images or multiframe GIF images requires a lot of RAM. If you cache an image, it still needs to be opened before displaying. When you close an image, all the memory used by the decoder, including any cached images, will be released. Calling the caching function does not guarantee that the image will be cached, for example, if there is not enough RAM. Since caching is fully optional, the image will still be drawn if you call the drawing function. It will simply be re-read from flash and re-decoded again. Image files in ROMFS ^^^^^^^^^^^^^^^^^^^^ ROMFS is the file system to store files in the code itself (usually in ROM/FLASH). To convert an image file into a header file, use the file2c tool. It can be found here: ``esp-iot-solution/components/hmi/ugfx_gui/ugfx/tools/file2c/src``. Navigate to the directory where the file2c tool is stored, run the make command, and then run ``./file2c -dcs image_flie header_flie``. Remember to replace ``image_flie`` and ``header_flie`` with real file names. To use the image, just include the header file into the ``romfs_files.h`` file of your project. Image formats ^^^^^^^^^^^^^ μGFX currently comes with the following image decoders: +--------------+-------------------------------------------------------------------------+ | **Format** | **Description** | +==============+=========================================================================+ | BMP | Including BMP1, BMP4, BMP4\_RLE, BMP8, BMP8\_RLE, BMP16, BMP24, BMP32 | +--------------+-------------------------------------------------------------------------+ | GIF | Including transparency and multi-frame support (animations) | +--------------+-------------------------------------------------------------------------+ | PNG | Including transparency and alpha support | +--------------+-------------------------------------------------------------------------+ | NATIVE | Uses the display drivers native format | +--------------+-------------------------------------------------------------------------+ For example: :: #include "iot_ugfx.h" /** * The image file must be stored on a GFILE file-system. * Use either GFILE_NEED_NATIVEFS or GFILE_NEED_ROMFS (or both). * * The ROMFS uses the file "romfs_files.h" to describe the set of files in the ROMFS. */ static gdispImage myImage; int main(void) { coord_t swidth, sheight; // Initialize uGFX and the underlying system gfxInit(); // Get the display dimensions swidth = gdispGetWidth(); sheight = gdispGetHeight(); // Set up IO for our image gdispImageOpenFile(&myImage, "myImage.bmp"); gdispImageDraw(&myImage, 0, 0, swidth, sheight, 0, 0); gdispImageClose(&myImage); while(1) { gfxSleepMilliseconds(1000); } return 0; } For detailed introduction, please refer to `Images `__. Default widget ~~~~~~~~~~~~~~ All the default widgets for µGFX GUI can be found in the above-mentioned `GWIN <#gwin>`__ module which also includes windows and containers. Windows ^^^^^^^ A window is the most basic GWIN element. All other elements, such as widgets and containers, are based on this one. A window has the following attributes: - Position - Size - Foreground color - Background color - Font Thus, a window is a completely passive element which does not accept any kind of input. Here are the current available windows: 1. Console Console is a rectangular window with a foreground and a background color. It currently does not accept any input and can only output text using ``gwinPrintf()``. Consoles can handle line breaks to wrap the text reaching the window's right border. The widget can also handle text scrolling which appears if text lines reach the window's bottom border. Console example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/console`` 2. Graph The graph window helps to easily draw curves and other sets of data with different colors and shapes in a rectangular window. Graph windows are not capable of taking any user input. Graph example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/graph`` Widgets ^^^^^^^ Widgets are based on windows. In addition to the window functionalities, a widget has the following features: - Supporting text attributes - Capable of redrawing - Accepting user input, e.g., from a touchscreen - Drawing functions can be overwritten, if there is a requirement for fancier and more sleek-looking objects. For example, along with the normal button drawing functions, there are predefined drawing functions for round buttons, image buttons, arrow buttons etc. - Supporting styles. By changing a style, you can change the color scheme used for drawing the widget, similar to the color schemes in Windows or Linux. Here are the current available widgets： 1. Label Label is a simple rectangular widget which takes no input. The label automatically redraws itself if the text is changed. If the label is smaller than the text it displays, the text gets clipped. To set the label text, use the function ``gwinSetText()``. 2. PushButton PushButton is a stand-alone widget with a static size and the text centered inside the button area. PushButtons have two states: *pressed* and *unpressed*. 3. RadioButton RadioButton is a widget that only works in a group of two or more RadioButtons. A group of RadioButtons can have only one button checked at a time. If you click on another RaidoButton, it gets checked, unchecking the previous one. 4. CheckBox Checkbox is a small stand-alone GUI element which has two states: *checked* and *unchecked*. By default, the text attribute of a checkbox is displayed on its left side. The width of the widget is supposed to be larger in order to contain text. 5. List List is a rectangular widget which contains multiple list entries, also known as items. An item is a simple string linked to a per-list unique ID. Through different inputs, such as a touchscreen, an item can be selected by directly touching it. Furthermore, the list widget automatically displays an Up- and a Down-Arrow on the right side for scrolling, if there are more items than can be displayed. If an empty section (below the last entry) of the list is touched, all selections are reset. A list can either be single- or multi-select. Also, it is possible to add small images to the left of the item string. Two images can be used - one for the selected state, the other for the unselected state. The following image shows the default drawing routine of the list widget. Please note that at this point you can replace the routines with your preferred custom rendering routine. The first list on the left is a normal single-selection list which shows the scrollbar. The second list in the middle is a multi-selection list, also with a scrollbar. The third image on the right shows a list with images drawn in front of the item text. It is a multi selection list without a scrollbar since all the list items fit the visible space. .. figure:: ../../_static/hmi_solution/ugfx/ugfx_gwin_list.jpg :align: center You can ensure that an item is visible in the list by using ``gwinListViewItem()``. 6. Slider Slider is a bar shaped GUI element with a handle that can be moved from the lowest (0) to the highest (100) value. The text attribute of the slider is displayed in the center of the slider bar. 7. Progressbar Progressbar is a rectangular box to visualize the progress of an operation. The progressbar widget can either be controlled manually or automatically. In both cases, the range of the progressbar can be changed through the function ``gwinProgressbarSetRange()``. The default values are 0 to 100. Furthermore, the resolution can be modified through the function ``gwinProgressbarSetResolution()``. This changes the size of the steps in which the progressbar will be incremented or decremented. The default resolution is 1. 8. ImageBox ImageBox uses the GDISP image decoder features and wraps them around a GWIN widget. ImageBox example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/imagebox`` 9. TextEdit TextEdit allows the user of a GUI to input text. The text input source can either be a physical keyboard (or keypad) interfaced through the GINPUT module or the virtual on-screen keyboard widget. TextEdit example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/textedit`` 10. Keyboard The keyboard widget provides a virtual on-screen keyboard. Keyboard can have a dynamically-changed layout. The widget comes with a set of built-in layouts such as QWERTY and NumPad. Although, you can also define custom layouts. Keyboard example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/keyboard`` TextEdit and Keyboard example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/textedit_virtual_keyboard`` Widgets example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/widgets`` Containers ^^^^^^^^^^ Containers are based on widgets. The main feature of a container is the ability to contain child windows that inherit the properties of their parent window. Here are the current available containers: 1. Container A basic container is a simple blank rectangle which can be used as a parent window to group widgets and contain them as children. To add a child widget to a container, add the container's GHandle to the child widget init structure: Container example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/container`` 2. Frame Frame is based on the container. It acts like a regular computer window. It has borders, a window title and an optional button to close it. Frame example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/frame`` 3. Tabset Tabset is a special container that manages different tabs, similar to web-browser tabs. You can create as many pages as you like and add widgets to each individual page. Please note that only the widgets on the active page will be visible to the user. This container is often used to create simple tab based menus. For this, a tabset is placed at the screen origin (``x = 0``, ``y = 0``) and covers the entire display size (``width = gdispGetWidth()``, ``height = gdispGetHeight()``). In order to avoid a border being drawn at the edge of the display, the value of the first parameter in the ``gwinTabsetCreate()`` function needs to be set to ``0``. Tabset example: ``/esp-iot-solution/components/hmi/ugfx_gui/ugfx/demos/modules/gwin/tabset`` FAQs ---- To track any possible program related issues, please check the return value of every single function. Images are not displayed ~~~~~~~~~~~~~~~~~~~~~~~~ Issue: The program seems to be compiled successfully and no error messages pop up when the program is running. Although, the image cannot be displayed. Please check the following: - Make sure that the display driver works properly and presents the basic widgets as usual. If not, make sure the correct IO and drivers are selected. - Check if the corresponding decoder is enabled in the configuration file. - Ensure that the image can be opened. - Make sure that the image decoder allocates enough memory. - Check if the limit for the number of opened files has been reached. If yes, the file from which you are loading the image cannot be opened. Please add ``GFILE_MAX_GFILES`` in the configuration file or close the opened files that are not in use.