RHI: compute viewport based on rendertarget size

So that behavior is consistent with the OpenGL renderer.
Computed viewport size is QViewport::normalizedRect * current render target
size. If current render target is the window, then its size is the same as
the surface size.

Change-Id: Icd8f8e18d8959ac045538b493fef690e3dd7221c
Reviewed-by: Mike Krus <mike.krus@kdab.com>
(cherry picked from commit 4794c7543726f2a460c9d16b0ae0154da39efd7c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 7 insertions, 6 deletions

diff --git a/src/plugins/renderers/rhi/renderer/renderer.cpp b/src/plugins/renderers/rhi/renderer/renderer.cpp
index 345fffdf8..4925fd251 100644
--- a/src/plugins/renderers/rhi/renderer/renderer.cpp
+++ b/src/plugins/renderers/rhi/renderer/renderer.cpp
@@ -2650,12 +2650,13 @@ bool Renderer::executeCommandsSubmission(const RHIPassInfo &passInfo)
         QRhiScissor scissor;
         bool hasScissor = false;
         {
-            const float x = rv->viewport().x() * rv->surfaceSize().width();
-            const float y = (1. - rv->viewport().y() - rv->viewport().height())
-                    * rv->surfaceSize().height();
-            const float w = rv->viewport().width() * rv->surfaceSize().width();
-            const float h = rv->viewport().height() * rv->surfaceSize().height();
-            //            qDebug() << x << y << w << h;
+            const QSize surfaceSize = rhiRenderTarget->pixelSize();
+
+            const float x = rv->viewport().x() * surfaceSize.width();
+            const float y = (1. - rv->viewport().y() - rv->viewport().height()) * surfaceSize.height();
+            const float w = rv->viewport().width() * surfaceSize.width();
+            const float h = rv->viewport().height() * surfaceSize.height();
+            // qDebug() << surfaceSize << x << y << w << h;
             vp = { x, y, w, h };
         }
         // Scissoring