Introduce PixelBuffer API to enable PBOs

PBOs (Pixel Buffer Objects) can be used on OpenGL ES 3.0 to perform
asynchronous texture uploads to free up the CPU. This change does not
enable the use of PBOs unless a specific property is set (Adreno drivers
have issues with PBOs at the moment, Mali drivers work just fine.)

This change also cleans up Font/FontRenderer a little bit and improves
performance of drop shadows generations by using memcpy() instead of
a manual byte-by-byte copy.

On GL ES 2.0 devices, or when PBOs are disabled, a PixelBuffer instance
behaves like a simple byte array. The extra APIs introduced for PBOs
(map/unmap and bind/unbind) are pretty much no-ops for CPU pixel
buffers and won't introduce any significant overhead.

This change also fixes a bug with text drop shadows: if the drop
shadow is larger than the max texture size, the renderer would leave
the GL context in a bad state and generate 0x501 errors. This change
simply skips drop shadows if they are too large.

Change-Id: I2700aadb0c6093431dc5dee3d587d689190c4e23

1 files changed, 4 insertions, 0 deletions

diff --git a/libs/hwui/TextDropShadowCache.cpp b/libs/hwui/TextDropShadowCache.cpp
index f1f35bd..6976eaa 100644
--- a/libs/hwui/TextDropShadowCache.cpp
+++ b/libs/hwui/TextDropShadowCache.cpp
@@ -178,6 +178,10 @@ ShadowTexture* TextDropShadowCache::get(SkPaint* paint, const char* text, uint32
         FontRenderer::DropShadow shadow = mRenderer->renderDropShadow(&paintCopy, text, 0,
                 len, numGlyphs, radius, positions);
 
+        if (!shadow.image) {
+            return NULL;
+        }
+
         texture = new ShadowTexture;
         texture->left = shadow.penX;
         texture->top = shadow.penY;