Downscale textures which exceed the GL texture limit

This way they will at least render.

[ChangeLog][QtQuick] Images exceeding GL_MAX_TEXTURE_SIZE will be
downscaled to fit so they will still show.

Change-Id: I169ecac768036812b8e14265ec1a0a8902655666
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

3 files changed, 29 insertions, 8 deletions

diff --git a/src/quick/scenegraph/qsgcontext.cpp b/src/quick/scenegraph/qsgcontext.cpp
index 6ebc479ec5..4e768574c4 100644
--- a/src/quick/scenegraph/qsgcontext.cpp
+++ b/src/quick/scenegraph/qsgcontext.cpp
@@ -253,6 +253,7 @@ void QSGContext::renderContextInitialized(QSGRenderContext *renderContext)
         QSet<QByteArray> exts = renderContext->openglContext()->extensions();
         QByteArray all; foreach (const QByteArray &e, exts) all += ' ' + e;
         qCDebug(QSG_LOG_INFO) << "GL_EXTENSIONS:    " << all.constData();
+        qCDebug(QSG_LOG_INFO) << "Max Texture Size: " << renderContext->maxTextureSize();
     }
 
     d->mutex.unlock();
@@ -392,6 +393,7 @@ QSGRenderContext::QSGRenderContext(QSGContext *context)
     , m_atlasManager(0)
     , m_depthStencilManager(0)
     , m_distanceFieldCacheManager(0)
+    , m_maxTextureSize(0)
     , m_brokenIBOs(false)
     , m_serializedRender(false)
     , m_attachToGLContext(true)
@@ -493,6 +495,9 @@ void QSGRenderContext::registerFontengineForCleanup(QFontEngine *engine)
  */
 void QSGRenderContext::initialize(QOpenGLContext *context)
 {
+    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();
+    funcs->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &m_maxTextureSize);
+
     // Sanity check the surface format, in case it was overridden by the application
     QSurfaceFormat requested = m_sg->defaultSurfaceFormat();
     QSurfaceFormat actual = context->format();
@@ -513,7 +518,6 @@ void QSGRenderContext::initialize(QOpenGLContext *context)
     m_sg->renderContextInitialized(this);
 
 #ifdef Q_OS_LINUX
-    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();
     const char *vendor = (const char *) funcs->glGetString(GL_VENDOR);
     if (strstr(vendor, "nouveau"))
         m_brokenIBOs = true;
diff --git a/src/quick/scenegraph/qsgcontext_p.h b/src/quick/scenegraph/qsgcontext_p.h
index b5271f9f37..70202264bf 100644
--- a/src/quick/scenegraph/qsgcontext_p.h
+++ b/src/quick/scenegraph/qsgcontext_p.h
@@ -126,6 +126,7 @@ public:
     static QSGRenderContext *from(QOpenGLContext *context);
 
     bool hasBrokenIndexBufferObjects() const { return m_brokenIBOs; }
+    int maxTextureSize() const { return m_maxTextureSize; }
 
 Q_SIGNALS:
     void initialized();
@@ -147,7 +148,7 @@ protected:
     QSGDistanceFieldGlyphCacheManager *m_distanceFieldCacheManager;
 
     QSet<QFontEngine *> m_fontEnginesToClean;
-
+    int m_maxTextureSize;
     bool m_brokenIBOs;
     bool m_serializedRender;
     bool m_attachToGLContext;
diff --git a/src/quick/scenegraph/util/qsgtexture.cpp b/src/quick/scenegraph/util/qsgtexture.cpp
index 69edfab379..abd9d480c5 100644
--- a/src/quick/scenegraph/util/qsgtexture.cpp
+++ b/src/quick/scenegraph/util/qsgtexture.cpp
@@ -671,12 +671,28 @@ void QSGPlainTexture::bind()
         bindTime = qsg_renderer_timer.nsecsElapsed();
 
     // ### TODO: check for out-of-memory situations...
-    int w = m_image.width();
-    int h = m_image.height();
 
     QImage tmp = (m_image.format() == QImage::Format_RGB32 || m_image.format() == QImage::Format_ARGB32_Premultiplied)
                  ? m_image
                  : m_image.convertToFormat(QImage::Format_ARGB32_Premultiplied);
+
+    // Downscale the texture to fit inside the max texture limit if it is too big.
+    // It would be better if the image was already downscaled to the right size,
+    // but this information is not always available at that time, so as a last
+    // resort we can do it here. Texture coordinates are normalized, so it
+    // won't cause any problems and actual texture sizes will be written
+    // based on QSGTexture::textureSize which is updated after this, so that
+    // should be ok.
+    int max;
+    if (QSGRenderContext *rc = QSGRenderContext::from(context))
+        max = rc->maxTextureSize();
+    else
+        glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max);
+    if (tmp.width() > max || tmp.height() > max) {
+        tmp = tmp.scaled(qMin(max, tmp.width()), qMin(max, tmp.height()), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
+        m_texture_size = tmp.size();
+    }
+
     if (tmp.width() * 4 != tmp.bytesPerLine())
         tmp = tmp.copy();
 
@@ -726,7 +742,7 @@ void QSGPlainTexture::bind()
     if (profileFrames)
         swizzleTime = qsg_renderer_timer.nsecsElapsed();
 
-    funcs->glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, w, h, 0, externalFormat, GL_UNSIGNED_BYTE, tmp.constBits());
+    funcs->glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, m_texture_size.width(), m_texture_size.height(), 0, externalFormat, GL_UNSIGNED_BYTE, tmp.constBits());
 
     qint64 uploadTime = 0;
     if (profileFrames)
@@ -741,7 +757,7 @@ void QSGPlainTexture::bind()
     if (profileFrames) {
         mipmapTime = qsg_renderer_timer.nsecsElapsed();
         qCDebug(QSG_LOG_TIME_TEXTURE,
-                "plain texture uploaded in: %dms (%dx%d), bind=%d, convert=%d, swizzle=%d (%s->%s), upload=%d, mipmap=%d",
+                "plain texture uploaded in: %dms (%dx%d), bind=%d, convert=%d, swizzle=%d (%s->%s), upload=%d, mipmap=%d%s",
                 int(mipmapTime / 1000000),
                 m_texture_size.width(), m_texture_size.height(),
                 int(bindTime / 1000000),
@@ -750,7 +766,8 @@ void QSGPlainTexture::bind()
                 (externalFormat == GL_BGRA ? "BGRA" : "RGBA"),
                 (internalFormat == GL_BGRA ? "BGRA" : "RGBA"),
                 int((uploadTime - swizzleTime)/1000000),
-                int((mipmapTime - uploadTime)/1000000));
+                int((mipmapTime - uploadTime)/1000000),
+                m_texture_size != m_image.size() ? " (scaled to GL_MAX_TEXTURE_SIZE)" : "");
     }
 
     Q_QUICK_SG_PROFILE(QQuickProfiler::SceneGraphTexturePrepare, (
@@ -760,7 +777,6 @@ void QSGPlainTexture::bind()
             uploadTime - swizzleTime,
             qsg_renderer_timer.nsecsElapsed() - uploadTime));
 
-    m_texture_size = QSize(w, h);
     m_texture_rect = QRectF(0, 0, 1, 1);
 
     m_dirty_bind_options = false;