From 2ccb46cebccc4a4655e660fbcbb876738c3639c7 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <slouken@libsdl.org>
Date: Sat, 1 Oct 2016 10:43:01 -0700
Subject: [PATCH] Fixed bug 3373 - OpenGL implementation differences of
 glDrawTexfOES

Simon Hug

It seems not everyone implemented glDrawTexfOES the same. Intel and Mesa ignore the viewport entirely, whereas the Raspberry Pi implementation offsets the coordinates and does viewport clipping.

The glDrawTexfOES extension text [1] for the function says "Xs and Ys are given directly in window (viewport) coordinates." I guess this wasn't clear enough.

Alex Szpakowski

Honestly I'd probably remove that codepath from SDL_Render entirely. It's an OpenGL ES 1-specific extension that isn't likely to give huge performance gains and adds additional maintenance overhead to SDL_Render while also having bugs in some drivers (as seen here).
---
 src/render/opengles/SDL_render_gles.c | 106 ++++++++------------------
 1 file changed, 31 insertions(+), 75 deletions(-)

diff --git a/src/render/opengles/SDL_render_gles.c b/src/render/opengles/SDL_render_gles.c
index 0d59da360..9f7969135 100644
--- a/src/render/opengles/SDL_render_gles.c
+++ b/src/render/opengles/SDL_render_gles.c
@@ -129,8 +129,6 @@ typedef struct
     GLES_FBOList *framebuffers;
     GLuint window_framebuffer;
 
-    SDL_bool useDrawTexture;
-    SDL_bool GL_OES_draw_texture_supported;
     SDL_bool GL_OES_blend_func_separate_supported;
 } GLES_RenderData;
 
@@ -369,19 +367,6 @@ GLES_CreateRenderer(SDL_Window * window, Uint32 flags)
         renderer->info.flags |= SDL_RENDERER_PRESENTVSYNC;
     }
 
-#if SDL_VIDEO_DRIVER_PANDORA
-    data->GL_OES_draw_texture_supported = SDL_FALSE;
-    data->useDrawTexture = SDL_FALSE;
-#else
-    if (SDL_GL_ExtensionSupported("GL_OES_draw_texture")) {
-        data->GL_OES_draw_texture_supported = SDL_TRUE;
-        data->useDrawTexture = SDL_TRUE;
-    } else {
-        data->GL_OES_draw_texture_supported = SDL_FALSE;
-        data->useDrawTexture = SDL_FALSE;
-    }
-#endif
-
     value = 0;
     data->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &value);
     renderer->info.max_texture_width = value;
@@ -952,71 +937,42 @@ GLES_RenderCopy(SDL_Renderer * renderer, SDL_Texture * texture,
 
     GLES_SetTexCoords(data, SDL_TRUE);
 
-    if (data->GL_OES_draw_texture_supported && data->useDrawTexture) {
-        /* this code is a little funny because the viewport is upside down vs SDL's coordinate system */
-        GLint cropRect[4];
-        int w, h;
-        SDL_Window *window = renderer->window;
+    minx = dstrect->x;
+    miny = dstrect->y;
+    maxx = dstrect->x + dstrect->w;
+    maxy = dstrect->y + dstrect->h;
 
-        SDL_GetWindowSize(window, &w, &h);
-        if (renderer->target) {
-            cropRect[0] = srcrect->x;
-            cropRect[1] = srcrect->y;
-            cropRect[2] = srcrect->w;
-            cropRect[3] = srcrect->h;
-            data->glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES,
-                                   cropRect);
-            data->glDrawTexfOES(renderer->viewport.x + dstrect->x, renderer->viewport.y + dstrect->y, 0,
-                                dstrect->w, dstrect->h);
-        } else {
-            cropRect[0] = srcrect->x;
-            cropRect[1] = srcrect->y + srcrect->h;
-            cropRect[2] = srcrect->w;
-            cropRect[3] = -srcrect->h;
-            data->glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_CROP_RECT_OES,
-                                   cropRect);
-            data->glDrawTexfOES(renderer->viewport.x + dstrect->x,
-                        h - (renderer->viewport.y + dstrect->y) - dstrect->h, 0,
-                        dstrect->w, dstrect->h);
-        }
-    } else {
+    minu = (GLfloat) srcrect->x / texture->w;
+    minu *= texturedata->texw;
+    maxu = (GLfloat) (srcrect->x + srcrect->w) / texture->w;
+    maxu *= texturedata->texw;
+    minv = (GLfloat) srcrect->y / texture->h;
+    minv *= texturedata->texh;
+    maxv = (GLfloat) (srcrect->y + srcrect->h) / texture->h;
+    maxv *= texturedata->texh;
 
-        minx = dstrect->x;
-        miny = dstrect->y;
-        maxx = dstrect->x + dstrect->w;
-        maxy = dstrect->y + dstrect->h;
+    vertices[0] = minx;
+    vertices[1] = miny;
+    vertices[2] = maxx;
+    vertices[3] = miny;
+    vertices[4] = minx;
+    vertices[5] = maxy;
+    vertices[6] = maxx;
+    vertices[7] = maxy;
 
-        minu = (GLfloat) srcrect->x / texture->w;
-        minu *= texturedata->texw;
-        maxu = (GLfloat) (srcrect->x + srcrect->w) / texture->w;
-        maxu *= texturedata->texw;
-        minv = (GLfloat) srcrect->y / texture->h;
-        minv *= texturedata->texh;
-        maxv = (GLfloat) (srcrect->y + srcrect->h) / texture->h;
-        maxv *= texturedata->texh;
+    texCoords[0] = minu;
+    texCoords[1] = minv;
+    texCoords[2] = maxu;
+    texCoords[3] = minv;
+    texCoords[4] = minu;
+    texCoords[5] = maxv;
+    texCoords[6] = maxu;
+    texCoords[7] = maxv;
 
-        vertices[0] = minx;
-        vertices[1] = miny;
-        vertices[2] = maxx;
-        vertices[3] = miny;
-        vertices[4] = minx;
-        vertices[5] = maxy;
-        vertices[6] = maxx;
-        vertices[7] = maxy;
+    data->glVertexPointer(2, GL_FLOAT, 0, vertices);
+    data->glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
+    data->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 
-        texCoords[0] = minu;
-        texCoords[1] = minv;
-        texCoords[2] = maxu;
-        texCoords[3] = minv;
-        texCoords[4] = minu;
-        texCoords[5] = maxv;
-        texCoords[6] = maxu;
-        texCoords[7] = maxv;
-
-        data->glVertexPointer(2, GL_FLOAT, 0, vertices);
-        data->glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
-        data->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
-    }
     data->glDisable(GL_TEXTURE_2D);
 
     return 0;