Improve framebuffer handling on Zephyr

src/Arduino_Video.cpp

@@ -56,6 +56,7 @@ static struct display_buffer_descriptor desc = {
   .frame_incomplete = false
 };
 uint16_t *buffer = nullptr;
+static uint8_t *framebuffer_base = nullptr;
 #endif
 
 Arduino_Video::Arduino_Video(int width, int height, DisplayShield &shield)
@@ -117,8 +118,8 @@ int Arduino_Video::begin() {
 #endif
 
   display_get_capabilities(display_dev, &display_caps);
-  _width = display_caps.y_resolution;
-  _height = display_caps.x_resolution;
+  _width = _rotated ? display_caps.y_resolution : display_caps.x_resolution;
+  _height = _rotated ? display_caps.x_resolution : display_caps.y_resolution;
 
   printk("- Capabilities:\n");
   printk("  x_resolution = %u, y_resolution = %u\n, supported_pixel_formats = %u\n"
@@ -127,19 +128,27 @@ int Arduino_Video::begin() {
          display_caps.supported_pixel_formats, display_caps.current_pixel_format,
          display_caps.current_orientation);
 
-  display_blanking_off(display_dev);
-
   void *ptrFB = display_get_framebuffer(display_dev);
   if (ptrFB == nullptr) {
     printk("Memory display allocation failed!");
     while (1) {}
   }
   // Cast the void pointer to an int pointer to use it
   buffer = static_cast<uint16_t *>(ptrFB);
+  if (framebuffer_base == nullptr) {
+    framebuffer_base = static_cast<uint8_t *>(ptrFB);
+  }
 
   display_blanking_on(display_dev);
+  if (display_caps.current_pixel_format == PIXEL_FORMAT_RGB_565) {
+    memset(framebuffer_base, 0, CONFIG_STM32_LTDC_FB_NUM * display_caps.x_resolution *
+           display_caps.y_resolution * sizeof(uint16_t));
+  }
+  display_blanking_off(display_dev);
 
-  setFrameDesc(width(), height(), width(), (width() * height() * sizeof(uint16_t)));
+  setFrameDesc(display_caps.x_resolution, display_caps.y_resolution,
+               display_caps.x_resolution,
+               display_caps.x_resolution * display_caps.y_resolution * sizeof(uint16_t));
 #else
   /* Video controller/bridge init */
   int err_code = _shield->init(_edidMode);
@@ -357,6 +366,22 @@ void *Arduino_Video::getFramebuffer() {
 }
 
 #if defined(ARDUINO_GIGA) && defined(__ZEPHYR__)
+void *Arduino_Video::getDrawBuffer() {
+  if (framebuffer_base == nullptr || display_caps.current_pixel_format != PIXEL_FORMAT_RGB_565) {
+    return nullptr;
+  }
+
+  uint8_t *front = static_cast<uint8_t *>(display_get_framebuffer(display_dev));
+  size_t bytes = display_caps.x_resolution * display_caps.y_resolution * sizeof(uint16_t);
+  for (int i = 0; i < CONFIG_STM32_LTDC_FB_NUM; i++) {
+    uint8_t *candidate = framebuffer_base + i * bytes;
+    if (candidate != front) {
+      return candidate;
+    }
+  }
+  return front;
+}
+
 void Arduino_Video::setFrameDesc(uint16_t w, uint16_t h, uint16_t pitch, uint32_t buf_size) {
   desc.buf_size = buf_size;
   desc.width = w;     /** Number of pixels between consecutive rows in the data buffer */

src/Arduino_Video.h

@@ -105,6 +105,16 @@ class Arduino_Video
   void *getFramebuffer();
 
 #if defined(__ZEPHYR__)
+  /**
+   * @brief Get a native RGB565 buffer for drawing, or nullptr if unavailable.
+   *
+   * Uses a non-displayed driver buffer when available, otherwise the displayed
+   * buffer (which may tear). Present it with drawBuffer(0, 0, buf).
+   * Buffer coordinates are native panel coordinates, without logical rotation.
+   * The pointer is owned by the driver and must not be freed.
+   */
+  void *getDrawBuffer();
+
   /**
    * @brief Set the frame descriptor for the display.
    *