SurfaceBackings are always zoomable once zoomable

Previously toggling hasText for the content of the SurfaceBacking was enough to
cause it to change scale entirely each time the value was changed. Now the
allowZoom flag is sticky to avoid unnecessary full-SurfaceBacking repaints.

Additionally, changes from allowZoom true->false will not trigger delay.

Change-Id: Ie6a13850f86d21f5a12a184c08b940aa2156ef07

1 files changed, 20 insertions, 8 deletions

diff --git a/Source/WebCore/platform/graphics/android/rendering/SurfaceBacking.cpp b/Source/WebCore/platform/graphics/android/rendering/SurfaceBacking.cpp
index d7f6535..5b11df6 100644
--- a/Source/WebCore/platform/graphics/android/rendering/SurfaceBacking.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/SurfaceBacking.cpp
@@ -40,13 +40,15 @@
 namespace WebCore {
 
 SurfaceBacking::SurfaceBacking(bool isBaseSurface)
+    : m_frontTileGrid(new TileGrid(isBaseSurface))
+    , m_backTileGrid(new TileGrid(isBaseSurface))
+    , m_lowResTileGrid(new TileGrid(isBaseSurface))
+    , m_scale(-1)
+    , m_futureScale(-1)
+    , m_zooming(false)
+    , m_hasAllowedZoom(false)
+
 {
-    m_frontTileGrid = new TileGrid(isBaseSurface);
-    m_backTileGrid = new TileGrid(isBaseSurface);
-    m_lowResTileGrid = new TileGrid(isBaseSurface);
-    m_scale = -1;
-    m_futureScale = -1;
-    m_zooming = false;
 #ifdef DEBUG_COUNT
     ClassTracker::instance()->increment("SurfaceBacking");
 #endif
@@ -67,9 +69,16 @@ void SurfaceBacking::prepareGL(GLWebViewState* state, bool allowZoom,
                                TilePainter* painter, bool aggressiveRendering,
                                bool updateWithBlit)
 {
+    // If the surface backing has ever zoomed beyond 1.0 scale, it's always
+    // allowed to (so repaints aren't necessary when allowZoom toggles). If not,
+    // and allowZoom is false, don't allow scale greater than 1.0
+    m_hasAllowedZoom |= allowZoom;
     float scale = state->scale();
-    if (scale > 1 && !allowZoom)
+    bool scaleOverridden = false;
+    if (scale > 1 && !m_hasAllowedZoom) {
         scale = 1;
+        scaleOverridden = true;
+    }
 
     if (m_scale == -1) {
         m_scale = scale;
@@ -78,7 +87,10 @@ void SurfaceBacking::prepareGL(GLWebViewState* state, bool allowZoom,
 
     if (m_futureScale != scale) {
         m_futureScale = scale;
-        m_zoomUpdateTime = WTF::currentTime() + SurfaceBacking::s_zoomUpdateDelay;
+        if (scaleOverridden)
+            m_zoomUpdateTime = 0; // start rendering immediately
+        else
+            m_zoomUpdateTime = WTF::currentTime() + SurfaceBacking::s_zoomUpdateDelay;
         m_zooming = true;
 
         // release back TileGrid's TileTextures, so they can be reused immediately