Refactor QTextureGlyphCache

Separate getting the glyph coordinates from actually making and
populating the cache. Calling populate() and fillInPendingGlyphs()
immediately after should be equivalent to the old code, except it might
have fewer reallocations of the texture since you will only create it
one per set of glyphs.

This mainly enables populating the GL glyph cache outside a GL context
and then actually drawing into it later, when the context has actually
been established.

Reviewed-by: Kim

1 files changed, 49 insertions, 13 deletions

diff --git a/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp b/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
index 5371c5e..e2ec8a1 100644
--- a/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
+++ b/src/opengl/gl2paintengineex/qtextureglyphcache_gl.cpp
@@ -52,39 +52,65 @@ QT_BEGIN_NAMESPACE
 extern Q_GUI_EXPORT bool qt_cleartype_enabled;
 #endif
 
-QGLTextureGlyphCache::QGLTextureGlyphCache(QGLContext *context, QFontEngineGlyphCache::Type type, const QTransform &matrix)
+QGLTextureGlyphCache::QGLTextureGlyphCache(const QGLContext *context, QFontEngineGlyphCache::Type type, const QTransform &matrix)
     : QImageTextureGlyphCache(type, matrix)
-    , ctx(context)
+    , ctx(0)
     , m_width(0)
     , m_height(0)
 {
-    // broken FBO readback is a bug in the SGX 1.3 and 1.4 drivers for the N900 where
-    // copying between FBO's is broken if the texture is either GL_ALPHA or POT. The
-    // workaround is to use a system-memory copy of the glyph cache for this device.
-    // Switching to NPOT and GL_RGBA would both cost a lot more graphics memory and
-    // be slower, so that is not desireable.
-    if (!ctx->d_ptr->workaround_brokenFBOReadBack)
-        glGenFramebuffers(1, &m_fbo);
-
-    connect(QGLSignalProxy::instance(), SIGNAL(aboutToDestroyContext(const QGLContext*)),
-            SLOT(contextDestroyed(const QGLContext*)));
+    if (context != 0)
+        setContext(context);
 }
 
 QGLTextureGlyphCache::~QGLTextureGlyphCache()
 {
+    cleanUpContext();
+}
+
+void QGLTextureGlyphCache::cleanUpContext()
+{
     if (ctx) {
         QGLShareContextScope scope(ctx);
 
         if (!ctx->d_ptr->workaround_brokenFBOReadBack)
             glDeleteFramebuffers(1, &m_fbo);
 
-        if (m_width || m_height)
+        if (m_width || m_height) {
             glDeleteTextures(1, &m_texture);
+            m_width = 0;
+            m_height = 0;
+            m_h = 0;
+        }
+
+        ctx = 0;
     }
 }
 
+void QGLTextureGlyphCache::setContext(const QGLContext *context)
+{
+    cleanUpContext();
+
+    ctx = context;
+
+    // broken FBO readback is a bug in the SGX 1.3 and 1.4 drivers for the N900 where
+    // copying between FBO's is broken if the texture is either GL_ALPHA or POT. The
+    // workaround is to use a system-memory copy of the glyph cache for this device.
+    // Switching to NPOT and GL_RGBA would both cost a lot more graphics memory and
+    // be slower, so that is not desireable.
+    if (!ctx->d_ptr->workaround_brokenFBOReadBack)
+        glGenFramebuffers(1, &m_fbo);
+
+    connect(QGLSignalProxy::instance(), SIGNAL(aboutToDestroyContext(const QGLContext*)),
+            SLOT(contextDestroyed(const QGLContext*)));
+}
+
 void QGLTextureGlyphCache::createTextureData(int width, int height)
 {
+    if (ctx == 0) {
+        qWarning("QGLTextureGlyphCache::createTextureData: Called with no context");
+        return;
+    }
+
     // create in QImageTextureGlyphCache baseclass is meant to be called
     // only to create the initial image and does not preserve the content,
     // so we don't call when this function is called from resize.
@@ -118,6 +144,11 @@ void QGLTextureGlyphCache::createTextureData(int width, int height)
 
 void QGLTextureGlyphCache::resizeTextureData(int width, int height)
 {
+    if (ctx == 0) {
+        qWarning("QGLTextureGlyphCache::resizeTextureData: Called with no context");
+        return;
+    }
+
     int oldWidth = m_width;
     int oldHeight = m_height;
 
@@ -213,6 +244,11 @@ void QGLTextureGlyphCache::resizeTextureData(int width, int height)
 
 void QGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph)
 {
+    if (ctx == 0) {
+        qWarning("QGLTextureGlyphCache::fillTexture: Called with no context");
+        return;
+    }
+
     if (ctx->d_ptr->workaround_brokenFBOReadBack) {
         QImageTextureGlyphCache::fillTexture(c, glyph);