QRhi: Allow negative viewport origin

Do not bound viewport rect to surface size, only scirror rect.
Modifying the viewport will move the view origin changing the
way the scene gets rendered.

Task-number: QTBUG-106082
Change-Id: I105516bd460af87727d0e73f580b8cf6b748d87f
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
(cherry picked from commit d46ad528727772362b710d68c27d963db81235c4)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

4 files changed, 33 insertions, 22 deletions

diff --git a/src/gui/rhi/qrhi_p_p.h b/src/gui/rhi/qrhi_p_p.h
index 2a0cb7d631..fbc8be2e95 100644
--- a/src/gui/rhi/qrhi_p_p.h
+++ b/src/gui/rhi/qrhi_p_p.h
@@ -224,7 +224,13 @@ private:
     friend class QRhiResourceUpdateBatchPrivate;
 };
 
-template<typename T, size_t N>
+enum QRhiTargetRectBoundMode
+{
+    UnBounded,
+    Bounded
+};
+
+template<QRhiTargetRectBoundMode boundingMode, typename T, size_t N>
 bool qrhi_toTopLeftRenderTargetRect(const QSize &outputSize, const std::array<T, N> &r,
                                     T *x, T *y, T *w, T *h)
 {
@@ -235,7 +241,7 @@ bool qrhi_toTopLeftRenderTargetRect(const QSize &outputSize, const std::array<T,
     // or height. We must handle all other input gracefully, clamping to a zero
     // width or height rect in the worst case, and ensuring the resulting rect
     // is inside the rendertarget's bounds because some APIs' validation/debug
-    // layers are allergic to out of bounds scissor or viewport rects.
+    // layers are allergic to out of bounds scissor rects.
 
     const T outputWidth = outputSize.width();
     const T outputHeight = outputSize.height();
@@ -247,20 +253,23 @@ bool qrhi_toTopLeftRenderTargetRect(const QSize &outputSize, const std::array<T,
 
     *x = r[0];
     *y = outputHeight - (r[1] + inputHeight);
-
-    const T widthOffset = *x < 0 ? -*x : 0;
-    const T heightOffset = *y < 0 ? -*y : 0;
-    *w = *x < outputWidth ? qMax<T>(0, inputWidth - widthOffset) : 0;
-    *h = *y < outputHeight ? qMax<T>(0, inputHeight - heightOffset) : 0;
-
-    *x = qBound<T>(0, *x, outputWidth - 1);
-    *y = qBound<T>(0, *y, outputHeight - 1);
-
-    if (*x + *w > outputWidth)
-        *w = qMax<T>(0, outputWidth - *x);
-    if (*y + *h > outputHeight)
-        *h = qMax<T>(0, outputHeight - *y);
-
+    *w = inputWidth;
+    *h = inputHeight;
+
+    if (boundingMode == Bounded) {
+        const T widthOffset = *x < 0 ? -*x : 0;
+        const T heightOffset = *y < 0 ? -*y : 0;
+        *w = *x < outputWidth ? qMax<T>(0, inputWidth - widthOffset) : 0;
+        *h = *y < outputHeight ? qMax<T>(0, inputHeight - heightOffset) : 0;
+
+        *x = qBound<T>(0, *x, outputWidth - 1);
+        *y = qBound<T>(0, *y, outputHeight - 1);
+
+        if (*x + *w > outputWidth)
+            *w = qMax<T>(0, outputWidth - *x);
+        if (*y + *h > outputHeight)
+            *h = qMax<T>(0, outputHeight - *y);
+    }
     return true;
 }
 
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index 0ac92e2266..89bfb57716 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -1090,7 +1090,7 @@ void QRhiD3D11::setViewport(QRhiCommandBuffer *cb, const QRhiViewport &viewport)
 
     // d3d expects top-left, QRhiViewport is bottom-left
     float x, y, w, h;
-    if (!qrhi_toTopLeftRenderTargetRect(outputSize, viewport.viewport(), &x, &y, &w, &h))
+    if (!qrhi_toTopLeftRenderTargetRect<UnBounded>(outputSize, viewport.viewport(), &x, &y, &w, &h))
         return;
 
     QD3D11CommandBuffer::Command &cmd(cbD->commands.get());
@@ -1112,7 +1112,7 @@ void QRhiD3D11::setScissor(QRhiCommandBuffer *cb, const QRhiScissor &scissor)
 
     // d3d expects top-left, QRhiScissor is bottom-left
     int x, y, w, h;
-    if (!qrhi_toTopLeftRenderTargetRect(outputSize, scissor.scissor(), &x, &y, &w, &h))
+    if (!qrhi_toTopLeftRenderTargetRect<Bounded>(outputSize, scissor.scissor(), &x, &y, &w, &h))
         return;
 
     QD3D11CommandBuffer::Command &cmd(cbD->commands.get());
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index bd761b4e15..33cdae7d35 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -1305,7 +1305,7 @@ void QRhiMetal::setViewport(QRhiCommandBuffer *cb, const QRhiViewport &viewport)
 
     // x,y is top-left in MTLViewportRect but bottom-left in QRhiViewport
     float x, y, w, h;
-    if (!qrhi_toTopLeftRenderTargetRect(outputSize, viewport.viewport(), &x, &y, &w, &h))
+    if (!qrhi_toTopLeftRenderTargetRect<UnBounded>(outputSize, viewport.viewport(), &x, &y, &w, &h))
         return;
 
     MTLViewport vp;
@@ -1320,6 +1320,7 @@ void QRhiMetal::setViewport(QRhiCommandBuffer *cb, const QRhiViewport &viewport)
 
     if (!QRHI_RES(QMetalGraphicsPipeline, cbD->currentGraphicsPipeline)->m_flags.testFlag(QRhiGraphicsPipeline::UsesScissor)) {
         MTLScissorRect s;
+        qrhi_toTopLeftRenderTargetRect<Bounded>(outputSize, viewport.viewport(), &x, &y, &w, &h);
         s.x = NSUInteger(x);
         s.y = NSUInteger(y);
         s.width = NSUInteger(w);
@@ -1337,7 +1338,7 @@ void QRhiMetal::setScissor(QRhiCommandBuffer *cb, const QRhiScissor &scissor)
 
     // x,y is top-left in MTLScissorRect but bottom-left in QRhiScissor
     int x, y, w, h;
-    if (!qrhi_toTopLeftRenderTargetRect(outputSize, scissor.scissor(), &x, &y, &w, &h))
+    if (!qrhi_toTopLeftRenderTargetRect<Bounded>(outputSize, scissor.scissor(), &x, &y, &w, &h))
         return;
 
     MTLScissorRect s;
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index bcf5dab117..fd1ede2424 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -4929,7 +4929,7 @@ void QRhiVulkan::setViewport(QRhiCommandBuffer *cb, const QRhiViewport &viewport
 
     // x,y is top-left in VkViewport but bottom-left in QRhiViewport
     float x, y, w, h;
-    if (!qrhi_toTopLeftRenderTargetRect(outputSize, viewport.viewport(), &x, &y, &w, &h))
+    if (!qrhi_toTopLeftRenderTargetRect<UnBounded>(outputSize, viewport.viewport(), &x, &y, &w, &h))
         return;
 
     QVkCommandBuffer::Command &cmd(cbD->commands.get());
@@ -4951,6 +4951,7 @@ void QRhiVulkan::setViewport(QRhiCommandBuffer *cb, const QRhiViewport &viewport
     if (!QRHI_RES(QVkGraphicsPipeline, cbD->currentGraphicsPipeline)->m_flags.testFlag(QRhiGraphicsPipeline::UsesScissor)) {
         QVkCommandBuffer::Command &cmd(cbD->commands.get());
         VkRect2D *s = &cmd.args.setScissor.scissor;
+        qrhi_toTopLeftRenderTargetRect<Bounded>(outputSize, viewport.viewport(), &x, &y, &w, &h);
         s->offset.x = int32_t(x);
         s->offset.y = int32_t(y);
         s->extent.width = uint32_t(w);
@@ -4973,7 +4974,7 @@ void QRhiVulkan::setScissor(QRhiCommandBuffer *cb, const QRhiScissor &scissor)
 
     // x,y is top-left in VkRect2D but bottom-left in QRhiScissor
     int x, y, w, h;
-    if (!qrhi_toTopLeftRenderTargetRect(outputSize, scissor.scissor(), &x, &y, &w, &h))
+    if (!qrhi_toTopLeftRenderTargetRect<Bounded>(outputSize, scissor.scissor(), &x, &y, &w, &h))
         return;
 
     QVkCommandBuffer::Command &cmd(cbD->commands.get());