gl: Check for image validity in readback

Returning a null QImage is preferable over passing a null bits()
to glReadPixels. (matters when QImage's malloc() gives null, thus
'd' is null -> isNull() == true)

Fixes: QTBUG-113127
Pick-to: 6.5 6.4 6.2 5.15
Change-Id: Ieca4d91eefdea47da5251dabe77cc31b48eb0e28
Reviewed-by: Allan Sandfeld Jensen <[email protected]>

1 files changed, 12 insertions, 6 deletions

diff --git a/src/opengl/qopenglframebufferobject.cpp b/src/opengl/qopenglframebufferobject.cpp
index ccb4f7b0a86..379c59a827d 100644
--- a/src/opengl/qopenglframebufferobject.cpp
+++ b/src/opengl/qopenglframebufferobject.cpp
@@ -1344,7 +1344,8 @@ static inline QImage qt_gl_read_framebuffer_rgba8(const QSize &size, bool includ
     bool isOpenGL12orBetter = !context->isOpenGLES() && (context->format().majorVersion() >= 2 || context->format().minorVersion() >= 2);
     if (isOpenGL12orBetter) {
         QImage img(size, include_alpha ? QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32);
-        funcs->glReadPixels(0, 0, w, h, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, img.bits());
+        if (!img.isNull())
+            funcs->glReadPixels(0, 0, w, h, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, img.bits());
         return img;
     }
 
@@ -1354,7 +1355,8 @@ static inline QImage qt_gl_read_framebuffer_rgba8(const QSize &size, bool includ
     // BGRA capable impl would return BGRA from there)
 
     QImage rgbaImage(size, include_alpha ? QImage::Format_RGBA8888_Premultiplied : QImage::Format_RGBX8888);
-    funcs->glReadPixels(0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, rgbaImage.bits());
+    if (!rgbaImage.isNull())
+        funcs->glReadPixels(0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, rgbaImage.bits());
     return rgbaImage;
 }
 
@@ -1362,7 +1364,8 @@ static inline QImage qt_gl_read_framebuffer_rgb10a2(const QSize &size, bool incl
 {
     // We assume OpenGL 1.2+ or ES 3.0+ here.
     QImage img(size, include_alpha ? QImage::Format_A2BGR30_Premultiplied : QImage::Format_BGR30);
-    context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_UNSIGNED_INT_2_10_10_10_REV, img.bits());
+    if (!img.isNull())
+        context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_UNSIGNED_INT_2_10_10_10_REV, img.bits());
     return img;
 }
 
@@ -1370,7 +1373,8 @@ static inline QImage qt_gl_read_framebuffer_rgba16(const QSize &size, bool inclu
 {
     // We assume OpenGL 1.2+ or ES 3.0+ here.
     QImage img(size, include_alpha ? QImage::Format_RGBA64_Premultiplied : QImage::Format_RGBX64);
-    context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_UNSIGNED_SHORT, img.bits());
+    if (!img.isNull())
+        context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_UNSIGNED_SHORT, img.bits());
     return img;
 }
 
@@ -1378,14 +1382,16 @@ static inline QImage qt_gl_read_framebuffer_rgba16f(const QSize &size, bool incl
 {
     // We assume OpenGL (ES) 3.0+ here.
     QImage img(size, include_alpha ? QImage::Format_RGBA16FPx4_Premultiplied : QImage::Format_RGBX16FPx4);
-    context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_HALF_FLOAT, img.bits());
+    if (!img.isNull())
+        context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_HALF_FLOAT, img.bits());
     return img;
 }
 
 static inline QImage qt_gl_read_framebuffer_rgba32f(const QSize &size, bool include_alpha, QOpenGLContext *context)
 {
     QImage img(size, include_alpha ? QImage::Format_RGBA32FPx4_Premultiplied : QImage::Format_RGBX32FPx4);
-    context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_FLOAT, img.bits());
+    if (!img.isNull())
+        context->functions()->glReadPixels(0, 0, size.width(), size.height(), GL_RGBA, GL_FLOAT, img.bits());
     return img;
 }