rg_display: Renamed RG_SCREEN_BYTE_ORDER to RG_SCREEN_PIXEL_FORMAT

It's quite conceivable that we'll eventually need to support more pixel formats than RGB565, and since byte order is intrinsically linked to the pixel format, we might as well just have a unified name.

It would make sense to unify the values with `RG_PIXEL_*` but it is an enum and would need to be replaced by defines first...

Author: ducalex

components/retro-go/rg_display.c

@@ -93,13 +93,13 @@ static inline unsigned blend_pixels(unsigned a, unsigned b)
 
     // Not the original author, but a good explanation is found at:
     // https://medium.com/@luc.trudeau/fast-averaging-of-high-color-16-bit-pixels-cb4ac7fd1488
-#if RG_SCREEN_BYTE_ORDER == 0
+#if RG_SCREEN_PIXEL_FORMAT == 0 /* 565_BE */
     a = (a << 8) | (a >> 8);
     b = (b << 8) | (b >> 8);
     unsigned s = a ^ b;
     unsigned v = ((s & 0xF7DEU) >> 1) + (a & b) + (s & 0x0821U);
     return (v << 8) | (v >> 8);
-#else
+#else /* 565_LE */
     unsigned s = a ^ b;
     return ((s & 0xF7DEU) >> 1) + (a & b) + (s & 0x0821U);
 #endif
@@ -191,13 +191,13 @@ static inline void write_update(const rg_surface_t *update)
             else
             {
                 #define RENDER_LINE(PTR_TYPE, PIXEL) { \
-                    PTR_TYPE *buffer = (PTR_TYPE *)(data + map_viewport_to_source_y[y] * stride);\
+                    const PTR_TYPE *buffer = (PTR_TYPE *)(data + map_viewport_to_source_y[y] * stride); \
                     for (int xx = 0; xx < draw_width; ++xx) { \
                         int x = map_viewport_to_source_x[xx]; \
                         *line_buffer_ptr++ = (PIXEL); \
                     } \
                 }
-            #if RG_SCREEN_BYTE_ORDER == 0
+            #if RG_SCREEN_PIXEL_FORMAT == 0 /* 565_BE */
                 if (format == RG_PIXEL_PAL565_BE)
                     RENDER_LINE(uint8_t, palette[buffer[x]])
                 else if (format == RG_PIXEL_565_BE)
@@ -206,7 +206,7 @@ static inline void write_update(const rg_surface_t *update)
                     RENDER_LINE(uint16_t, (buffer[x] << 8) | (buffer[x] >> 8))
                 else if (format == RG_PIXEL_PAL565_LE)
                     RENDER_LINE(uint8_t, (palette[buffer[x]] << 8) | (palette[buffer[x]] >> 8))
-            #else
+            #else /* 565_LE */
                 if (format == RG_PIXEL_PAL565_LE)
                     RENDER_LINE(uint8_t, palette[buffer[x]])
                 else if (format == RG_PIXEL_565_LE)
@@ -337,6 +337,7 @@ static void update_viewport_scaling(void)
     display.viewport.step_x = (float)src_width / display.viewport.width;
     display.viewport.step_y = (float)src_height / display.viewport.height;
 
+    // For a filter to be applied it has to be enabled in the menu and scaling factor can't be an integer
     display.viewport.filter_x = (config.filter == RG_DISPLAY_FILTER_HORIZ || config.filter == RG_DISPLAY_FILTER_BOTH) &&
                                 (config.scaling && (display.viewport.width % src_width) != 0);
     display.viewport.filter_y = (config.filter == RG_DISPLAY_FILTER_VERT || config.filter == RG_DISPLAY_FILTER_BOTH) &&
@@ -605,9 +606,9 @@ void rg_display_write_rect(int left, int top, int width, int height, int stride,
         {
             const uint16_t *src = (void *)buffer + ((y + line) * stride);
             uint16_t *dst = lcd_buffer + (line * width);
-        #if RG_SCREEN_BYTE_ORDER == 0
+        #if RG_SCREEN_PIXEL_FORMAT == 0 /* 565_BE */
             if ((flags & RG_DISPLAY_WRITE_BE_DATA) != 0)
-        #else
+        #else /* 565_LE */
             if ((flags & RG_DISPLAY_WRITE_BE_DATA) == 0)
         #endif
             {
@@ -639,9 +640,9 @@ void rg_display_clear_rect(int left, int top, int width, int height, uint16_t co
 {
     const int screen_left = display.screen.margins.left + left;
     const int screen_top = display.screen.margins.top + top;
-#if RG_SCREEN_BYTE_ORDER == 0
+#if RG_SCREEN_PIXEL_FORMAT == 0 /* 565_BE */
     const uint16_t color = (color_le << 8) | (color_le >> 8);
-#else
+#else /* 565_LE */
     const uint16_t color = color_le;
 #endif
 #if !LCD_SCREEN_BUFFER
@@ -701,6 +702,7 @@ bool rg_display_set_geometry(int width, int height, const rg_margins_t *margins)
     display.screen.margins = margins ? *margins : (rg_margins_t){0, 0, 0, 0};
     display.screen.width = display.screen.real_width - (display.screen.margins.left + display.screen.margins.right);
     display.screen.height = display.screen.real_height - (display.screen.margins.top + display.screen.margins.bottom);
+    // display.screen.format = RG_PIXEL_565_BE;
     display.changed = true;
     // update_viewport_scaling();             // This will be implicitly done by the display task
     rg_gui_update_geometry();              // Let the GUI know that the geometry has changed