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Bug 3406

Summary: Fix Reading Pixels from a SDL_TEXTUREACCESS_TARGET Texture
Product: SDL Reporter: ancientcc
Component: renderAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: sylvain.becker
Version: HG 2.1   
Hardware: All   
OS: All   
Attachments: Fix when use openGL

Description ancientcc 2016-08-09 13:51:38 UTC 
Created attachment 2548 [details]
Fix when use openGL

If use SDL_RenderReadPixels from SDL_TEXTUREACCESS_TARGET, will be fail. 

Attachment can solve it when Render with OpenGL. On the other handle, https://github.com/freeors/SDL/blob/master/SDL2-2.0.4/src/render/opengles2/SDL_render_gles2.c is responsing to OpenGL ES2.
Comment 1 Sam Lantinga 2016-10-01 20:11:22 UTC 
Can you please try with the latest SDL snapshot?
http://www.libsdl.org/tmp/SDL-2.0.zip
Comment 2 Sylvain 2017-11-09 14:55:27 UTC 
I tried and I mark this as fixed as it worked.

This was fixed by https://hg.libsdl.org/SDL/rev/b8ca95a8eea9

The provided file is based on SDL 2.0.4 and the diff is:

diff -r e12c38730512 src/render/opengl/SDL_render_gl.c
--- a/src/render/opengl/SDL_render_gl.c	Sat Jan 02 11:17:06 2016 -0800
+++ b/src/render/opengl/SDL_render_gl.c	Thu Nov 09 12:55:15 2017 +0100
@@ -1420,13 +1420,20 @@
 
     GL_ActivateRenderer(renderer);
 
-    temp_pitch = rect->w * SDL_BYTESPERPIXEL(temp_format);
-    temp_pixels = SDL_malloc(rect->h * temp_pitch);
-    if (!temp_pixels) {
-        return SDL_OutOfMemory();
+	if (renderer->target) {
+		// when target, its format and row rang is decided by app.
+		// only read data, let app process format and row rang.
+        temp_pitch = pitch;
+        temp_pixels = pixels;
+        temp_format = pixel_format;
+    } else {
+	    temp_pitch = rect->w * SDL_BYTESPERPIXEL(temp_format);
+        temp_pixels = SDL_malloc(rect->h * temp_pitch);
+        if (!temp_pixels) {
+            return SDL_OutOfMemory();
+        }
     }
-
-    convert_format(data, temp_format, &internalFormat, &format, &type);
+	convert_format(data, temp_format, &internalFormat, &format, &type);
 
     SDL_GetRendererOutputSize(renderer, &w, &h);
 
@@ -1434,7 +1441,7 @@
     data->glPixelStorei(GL_PACK_ROW_LENGTH,
                         (temp_pitch / SDL_BYTESPERPIXEL(temp_format)));
 
-    data->glReadPixels(rect->x, (h-rect->y)-rect->h, rect->w, rect->h,
+    data->glReadPixels(rect->x, renderer->target? rect->y: (h-rect->y)-rect->h, rect->w, rect->h,
                        format, type, temp_pixels);
 
     if (GL_CheckError("glReadPixels()", renderer) < 0) {
@@ -1442,6 +1449,10 @@
         return -1;
     }
 
+	if (renderer->target) {
+        return 0;
+    }
+
     /* Flip the rows to be top-down */
     length = rect->w * SDL_BYTESPERPIXEL(temp_format);
     src = (Uint8*)temp_pixels + (rect->h-1)*temp_pitch;