rgb_lcd: Preserve full framebuffer across region updates and raw draws

When update_region, draw_rgb565_raw, or the RLE cover path write only
their target region to the work framebuffer and then switch to it,
the rest of the screen content is lost because the work FB contains
stale data.

Fix: copy the full active framebuffer to the work FB before writing
the region pixels, so the entire screen state is preserved across
all framebuffer switches.

Signed-off-by: Ibrahim YILMAZ <ibrahim@drlinux.org>

Author: drlinux

rgb_lcd_display_driver.c

@@ -518,8 +518,16 @@ static void do_update_region(Context *ctx, int x0, int y0, int width, int height
 
     if (driver->framebuffer_count > 1) {
         int work_fb = select_work_framebuffer(driver);
-        if (work_fb >= 0
-                && render_items_to_framebuffer(driver, work_fb, x0, y0, width, height, items, len)) {
+        if (work_fb >= 0) {
+            // Copy entire active framebuffer to the work buffer so content
+            // outside the updated region (e.g. cover image drawn via
+            // draw_rgb565_raw) is preserved across framebuffer switches.
+            uint16_t *active_fb = active_framebuffer(driver);
+            if (active_fb) {
+                size_t fb_bytes = (size_t) driver->screen.w * (size_t) driver->screen.h * sizeof(uint16_t);
+                memcpy(driver->framebuffers[work_fb], active_fb, fb_bytes);
+            }
+            if (render_items_to_framebuffer(driver, work_fb, x0, y0, width, height, items, len)) {
             esp_err_t err = switch_to_framebuffer(driver, work_fb);
             if (err != ESP_OK) {
                 ESP_LOGE(TAG, "region framebuffer switch failed: %s", esp_err_to_name(err));
@@ -710,6 +718,11 @@ static void do_draw_rgb565_rle_base64_scaled(
                 ESP_LOGE(TAG, "cover framebuffer select failed.");
                 return;
             }
+            uint16_t *active_fb = active_framebuffer(driver);
+            if (active_fb) {
+                size_t fb_bytes = (size_t) driver->screen.w * (size_t) driver->screen.h * sizeof(uint16_t);
+                memcpy(driver->framebuffers[work_fb], active_fb, fb_bytes);
+            }
             copy_rgb565_region_to_framebuffer(driver, work_fb, x, y, draw_width, draw_height, draw_pixels);
             esp_err_t err = switch_to_framebuffer(driver, work_fb);
             if (err != ESP_OK) {
@@ -827,6 +840,13 @@ static void process_message(Message *message, Context *ctx)
                 ESP_LOGE(TAG, "draw_rgb565_raw: framebuffer select failed.");
                 return;
             }
+            // Copy full active framebuffer to work buffer so the rest of
+            // the screen (info, progress, controls) is preserved.
+            uint16_t *active_fb = active_framebuffer(driver);
+            if (active_fb) {
+                size_t fb_bytes = (size_t) driver->screen.w * (size_t) driver->screen.h * sizeof(uint16_t);
+                memcpy(driver->framebuffers[work_fb], active_fb, fb_bytes);
+            }
             copy_rgb565_region_to_framebuffer(driver, work_fb, x, y, width, height, (const uint16_t *) raw);
             esp_err_t err = switch_to_framebuffer(driver, work_fb);
             if (err != ESP_OK) {