From 0908764b2b3cf5075df4178a5f0a8547dcb7b317 Mon Sep 17 00:00:00 2001
From: Romain Guy <romainguy@google.com>
Date: Thu, 4 Apr 2013 12:27:54 -0700
Subject: First OpenGL ES 3.0 based optimization

This change uses a new OpenGL ES 3.0 feature to upload less data when
the font cache needs to be update. This can result in significant
performance improvements on device with large textures or with locales
that use a lot of glyphs (CJK for instance.)

This change also fixes various unpack alignment issues. The unpack
alignment, as well as the unpack row length, is not texture specific
but a global state that affect all glTex/SubImage2D calls. Some of
them were missing the appropriate glPixelStorei() call. This could
result in corrupted textures.

Change-Id: Iefb429d4d0d0b4e0faeadf27daafee6d30a21d85
---
 libs/hwui/FontRenderer.cpp | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

(limited to 'libs/hwui/FontRenderer.cpp')

diff --git a/libs/hwui/FontRenderer.cpp b/libs/hwui/FontRenderer.cpp
index 26c7e5d1ad6f..44dc731c6be7 100644
--- a/libs/hwui/FontRenderer.cpp
+++ b/libs/hwui/FontRenderer.cpp
@@ -31,6 +31,7 @@
 
 #include "Caches.h"
 #include "Debug.h"
+#include "Extensions.h"
 #include "FontRenderer.h"
 #include "Rect.h"
 
@@ -375,34 +376,60 @@ void FontRenderer::checkTextureUpdate() {
 
     Caches& caches = Caches::getInstance();
     GLuint lastTextureId = 0;
+
+    // OpenGL ES 3.0+ lets us specify the row length for unpack operations such
+    // as glTexSubImage2D(). This allows us to upload a sub-rectangle of a texture.
+    // With OpenGL ES 2.0 we have to upload entire stripes instead.
+    const bool hasUnpackRowLength = Extensions::getInstance().getMajorGlVersion() >= 3;
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
     // Iterate over all the cache textures and see which ones need to be updated
     for (uint32_t i = 0; i < mCacheTextures.size(); i++) {
         CacheTexture* cacheTexture = mCacheTextures[i];
         if (cacheTexture->isDirty() && cacheTexture->getTexture()) {
-            // Can't copy inner rect; glTexSubimage expects pointer to deal with entire buffer
-            // of data. So expand the dirty rect to the encompassing horizontal stripe.
             const Rect* dirtyRect = cacheTexture->getDirtyRect();
-            uint32_t x = 0;
+            uint32_t x = hasUnpackRowLength ? dirtyRect->left : 0;
             uint32_t y = dirtyRect->top;
             uint32_t width = cacheTexture->getWidth();
             uint32_t height = dirtyRect->getHeight();
-            void* textureData = cacheTexture->getTexture() + y * width;
+            void* textureData = cacheTexture->getTexture() + y * width + x;
 
             if (cacheTexture->getTextureId() != lastTextureId) {
                 lastTextureId = cacheTexture->getTextureId();
                 caches.activeTexture(0);
                 glBindTexture(GL_TEXTURE_2D, lastTextureId);
+
+                // The unpack row length only needs to be specified when a new
+                // texture is bound
+                if (hasUnpackRowLength) {
+                    glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
+                }
+            }
+
+            // If we can upload a sub-rectangle, use the dirty rect width
+            // instead of the width of the entire texture
+            if (hasUnpackRowLength) {
+                width = dirtyRect->getWidth();
             }
+
 #if DEBUG_FONT_RENDERER
             ALOGD("glTexSubimage for cacheTexture %d: x, y, width height = %d, %d, %d, %d",
                     i, x, y, width, height);
 #endif
+
             glTexSubImage2D(GL_TEXTURE_2D, 0, x, y, width, height,
                     GL_ALPHA, GL_UNSIGNED_BYTE, textureData);
+
             cacheTexture->setDirty(false);
         }
     }
 
+    // Reset to default unpack row length to avoid affecting texture
+    // uploads in other parts of the renderer
+    if (hasUnpackRowLength) {
+        glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+    }
+
     mUploadTexture = false;
 }
 
-- 
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