From 51433b94f074de7287bcdd064996d9809c9e0de9 Mon Sep 17 00:00:00 2001
From: Patrik Torstensson <totte@google.com>
Date: Sat, 30 Jan 2021 18:16:25 -0800
Subject: minui: Add support for ARGB (LSB alpha)

- Called RGBA to follow convention in minui
  where big-endian description of format is used
  and to avoid conflict with existing ARGB
- Handle alpha being LSB in png and text rendering

Change-Id: I0d9afef55aad05028ed0b8b4204f1d52aaa683c3
(cherry picked from commit cd1c327427febe7cf76e6fa4835847f0d4f398e3)
---
 minui/resources.cpp | 56 ++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 40 insertions(+), 16 deletions(-)

(limited to 'minui/resources.cpp')

diff --git a/minui/resources.cpp b/minui/resources.cpp
index d7b927700..1521c8f17 100644
--- a/minui/resources.cpp
+++ b/minui/resources.cpp
@@ -153,32 +153,57 @@ static void TransformRgbToDraw(const uint8_t* input_row, uint8_t* output_row, in
                                int width) {
   const uint8_t* ip = input_row;
   uint8_t* op = output_row;
+  PixelFormat pixel_format = gr_pixel_format();
 
   switch (channels) {
     case 1:
       // expand gray level to RGBX
       for (int x = 0; x < width; ++x) {
-        *op++ = *ip;
-        *op++ = *ip;
-        *op++ = *ip;
-        *op++ = 0xff;
+        if (pixel_format == PixelFormat::RGBA) {
+          *op++ = 0xff;
+          *op++ = *ip;
+          *op++ = *ip;
+          *op++ = *ip;
+        } else {
+          *op++ = *ip;
+          *op++ = *ip;
+          *op++ = *ip;
+          *op++ = 0xff;
+        }
         ip++;
       }
       break;
 
     case 3:
-      // expand RGBA to RGBX
       for (int x = 0; x < width; ++x) {
-        *op++ = *ip++;
-        *op++ = *ip++;
-        *op++ = *ip++;
-        *op++ = 0xff;
+        // expand RGBA to RGBX
+        if (pixel_format == PixelFormat::RGBA) {
+            *op++ = 0xff;
+            *op++ = *ip++;
+            *op++ = *ip++;
+            *op++ = *ip++;
+        } else {
+            *op++ = *ip++;
+            *op++ = *ip++;
+            *op++ = *ip++;
+            *op++ = 0xff;
+        }
       }
       break;
 
     case 4:
-      // copy RGBA to RGBX
-      memcpy(output_row, input_row, width * 4);
+      if (pixel_format == PixelFormat::RGBA) {
+        for (int x = 0; x < width; ++x) {
+            *op++ = *(ip + 3);
+            *op++ = *ip++;
+            *op++ = *ip++;
+            *op++ = *ip++;
+            ip++;
+        }
+      } else {
+        // copy RGBA to RGBX
+        memcpy(output_row, input_row, width * 4);
+      }
       break;
   }
 }
@@ -201,6 +226,8 @@ int res_create_display_surface(const char* name, GRSurface** pSurface) {
   PixelFormat pixel_format = gr_pixel_format();
   if (pixel_format == PixelFormat::ARGB || pixel_format == PixelFormat::BGRA) {
     png_set_bgr(png_ptr);
+  } else if (pixel_format == PixelFormat::RGBA) {
+    png_set_swap_alpha(png_ptr);
   }
 
   for (png_uint_32 y = 0; y < height; ++y) {
@@ -273,6 +300,8 @@ int res_create_multi_display_surface(const char* name, int* frames, int* fps,
 
   if (gr_pixel_format() == PixelFormat::ARGB || gr_pixel_format() == PixelFormat::BGRA) {
     png_set_bgr(png_ptr);
+  } else if (gr_pixel_format() == PixelFormat::RGBA) {
+    png_set_swap_alpha(png_ptr);
   }
 
   for (png_uint_32 y = 0; y < height; ++y) {
@@ -316,11 +345,6 @@ int res_create_alpha_surface(const char* name, GRSurface** pSurface) {
     return -8;
   }
 
-  PixelFormat pixel_format = gr_pixel_format();
-  if (pixel_format == PixelFormat::ARGB || pixel_format == PixelFormat::BGRA) {
-    png_set_bgr(png_ptr);
-  }
-
   for (png_uint_32 y = 0; y < height; ++y) {
     uint8_t* p_row = surface->data() + y * surface->row_bytes;
     png_read_row(png_ptr, p_row, nullptr);
-- 
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