From 08ba1ad14eeba6b6410b061c62bfcf7f005f1f56 Mon Sep 17 00:00:00 2001
From: Themaister <maister@archlinux.us>
Date: Wed, 1 Jan 2014 21:42:31 +0100
Subject: [PATCH] Use GL_RGB565 internal format when available.

This is a feature from ES2_compat extension.
It fixes the speed issue associated with using 16-bit textures on
desktop GL. Improves performance a bit as well as there's less bandwidth
usage during shading.

On my HD3000 laptop, performance improved with ~10%.
---
 gfx/gl.c        | 25 ++++++++++++++++++++++---
 gfx/gl_common.h | 17 ++++++++++++++---
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/gfx/gl.c b/gfx/gl.c
index a91409685c..d286f54941 100644
--- a/gfx/gl.c
+++ b/gfx/gl.c
@@ -1268,11 +1268,17 @@ static inline void gl_copy_frame(void *data, const void *frame, unsigned width,
    glPixelStorei(GL_UNPACK_ALIGNMENT, get_alignment(pitch));
    if (gl->base_size == 2)
    {
-      // Always use 32-bit textures on desktop GL.
-      gl_convert_frame_rgb16_32(gl, gl->conv_buffer, frame, width, height, pitch);
+      const void *buf = frame;
+      if (!gl->have_es2_compat)
+      {
+         // Convert to 32-bit textures on desktop GL.
+         gl_convert_frame_rgb16_32(gl, gl->conv_buffer, frame, width, height, pitch);
+         buf = gl->conv_buffer;
+      }
+
       glTexSubImage2D(GL_TEXTURE_2D,
             0, 0, 0, width, height, gl->texture_type,
-            gl->texture_fmt, gl->conv_buffer);
+            gl->texture_fmt, buf);
    }
    else
    {
@@ -1666,6 +1672,9 @@ static bool resolve_extensions(gl_t *gl)
       RARCH_ERR("[GL]: Failed to init VAOs.\n");
       return false;
    }
+
+   // GL_RGB565 internal format support.
+   gl->have_es2_compat = gl_query_extension(gl, "ARB_ES2_compatibility");
 #endif
 
 #ifdef HAVE_GL_SYNC
@@ -1743,6 +1752,16 @@ static inline void gl_set_texture_fmts(void *data, bool rgb32)
       gl->internal_fmt = GL_RGBA;
       gl->texture_type = GL_RGBA;
    }
+
+#ifndef HAVE_OPENGLES
+   if (!rgb32 && gl->have_es2_compat) // Use GL_RGB565 instead.
+   {
+      RARCH_LOG("[GL]: Using GL_RGB565 for texture uploads.\n");
+      gl->internal_fmt = RARCH_GL_INTERNAL_FORMAT16_565;
+      gl->texture_type = RARCH_GL_TEXTURE_TYPE16_565;
+      gl->texture_fmt = RARCH_GL_FORMAT16_565;
+   }
+#endif
 }
 
 static inline void gl_reinit_textures(void *data, const video_info_t *video)
diff --git a/gfx/gl_common.h b/gfx/gl_common.h
index e6b60d756d..99cc677204 100644
--- a/gfx/gl_common.h
+++ b/gfx/gl_common.h
@@ -212,6 +212,8 @@ typedef struct gl
    unsigned base_size; // 2 or 4
 #ifdef HAVE_OPENGLES
    bool support_unpack_row_length;
+#else
+   bool have_es2_compat;
 #endif
 
    // Fonts
@@ -266,7 +268,7 @@ typedef struct gl
 
 #if defined(HAVE_PSGL)
 #define RARCH_GL_INTERNAL_FORMAT32 GL_ARGB_SCE
-#define RARCH_GL_INTERNAL_FORMAT16 GL_RGB5
+#define RARCH_GL_INTERNAL_FORMAT16 GL_RGB5 // TODO: Verify if this is really 565 or just 555.
 #define RARCH_GL_TEXTURE_TYPE32 GL_BGRA
 #define RARCH_GL_TEXTURE_TYPE16 GL_BGRA
 #define RARCH_GL_FORMAT32 GL_UNSIGNED_INT_8_8_8_8_REV
@@ -288,12 +290,21 @@ typedef struct gl
 #define RARCH_GL_FORMAT16 GL_UNSIGNED_SHORT_5_6_5
 #else
 // On desktop, we always use 32-bit.
-#define RARCH_GL_INTERNAL_FORMAT32 GL_RGBA
-#define RARCH_GL_INTERNAL_FORMAT16 GL_RGBA
+#define RARCH_GL_INTERNAL_FORMAT32 GL_RGBA8
+#define RARCH_GL_INTERNAL_FORMAT16 GL_RGBA8
 #define RARCH_GL_TEXTURE_TYPE32 GL_BGRA
 #define RARCH_GL_TEXTURE_TYPE16 GL_BGRA
 #define RARCH_GL_FORMAT32 GL_UNSIGNED_INT_8_8_8_8_REV
 #define RARCH_GL_FORMAT16 GL_UNSIGNED_INT_8_8_8_8_REV
+
+// GL_RGB565 internal format isn't in desktop GL until 4.1 core (ARB_ES2_compatibility).
+// Check for this.
+#ifndef GL_RGB565
+#define GL_RGB565 0x8D62
+#endif
+#define RARCH_GL_INTERNAL_FORMAT16_565 GL_RGB565
+#define RARCH_GL_TEXTURE_TYPE16_565 GL_RGB
+#define RARCH_GL_FORMAT16_565 GL_UNSIGNED_SHORT_5_6_5
 #endif
 
 // Platform specific workarounds/hacks.