Add possibility to mirror ShaderEffectSource generated textures

Using textures generated by ShaderEffectSource items (or Item.layer)
with custom OpenGL code was non-intuitive due to mismatching coordinate
systems, so added a possibility to control the generated texture
orientation.

[ChangeLog][QtQuick][ShaderEffectSource] Added possibility to mirror
generated OpenGL texture.

Change-Id: I7c03d8b6fbfc43d69812c15d244200fb8e7c7bb9
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

1 files changed, 159 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickitemlayer/data/TextureMirroring.qml b/tests/auto/quick/qquickitemlayer/data/TextureMirroring.qml
new file mode 100644
index 0000000000..2827960153
--- /dev/null
+++ b/tests/auto/quick/qquickitemlayer/data/TextureMirroring.qml
@@ -0,0 +1,159 @@
+import QtQuick 2.6
+
+Item
+{
+    width: 250
+    height: 50
+
+    property int mirroring: 0
+
+    // Layered box without effect. Mirroring should not affect how it looks.
+    Rectangle {
+        x: 0
+        y: 0
+        width: 50
+        height: 50
+        layer.enabled: true
+        layer.textureMirroring: mirroring
+        Rectangle {
+            x: 0
+            y: 0
+            width: 25
+            height: 25
+            color: "#000000"
+        }
+        Rectangle {
+            x: 25
+            y: 0
+            width: 25
+            height: 25
+            color: "#ff0000"
+        }
+        Rectangle {
+            x: 0
+            y: 25
+            width: 25
+            height: 25
+            color: "#00ff00"
+        }
+        Rectangle {
+            x: 25
+            y: 25
+            width: 25
+            height: 25
+            color: "#0000ff"
+        }
+    }
+
+    // Layered box with effect. Mirroring should affect how it looks.
+    Rectangle {
+        id: layeredEffectBox
+        x: 50
+        y: 0
+        width: 50
+        height: 50
+        layer.enabled: true
+        layer.textureMirroring: mirroring
+        layer.samplerName: "source"
+        layer.effect: ShaderEffect {
+            property variant source: layeredEffectBox
+            fragmentShader: "
+                uniform lowp sampler2D source;
+                varying highp vec2 qt_TexCoord0;
+                void main() {
+                    gl_FragColor = texture2D(source, qt_TexCoord0);
+                }"
+
+        }
+
+        Rectangle {
+            x: 0
+            y: 0
+            width: 25
+            height: 25
+            color: "#000000"
+        }
+        Rectangle {
+            x: 25
+            y: 0
+            width: 25
+            height: 25
+            color: "#ff0000"
+        }
+        Rectangle {
+            x: 0
+            y: 25
+            width: 25
+            height: 25
+            color: "#00ff00"
+        }
+        Rectangle {
+            x: 25
+            y: 25
+            width: 25
+            height: 25
+            color: "#0000ff"
+        }
+    }
+
+    // Non-layered source item for ShaderEffectSource. Mirroring should not affect how it looks.
+    Rectangle {
+        id: box2
+        x: 100
+        y: 0
+        width: 50
+        height: 50
+        Rectangle {
+            x: 0
+            y: 0
+            width: 25
+            height: 25
+            color: "#000000"
+        }
+        Rectangle {
+            x: 25
+            y: 0
+            width: 25
+            height: 25
+            color: "#ff0000"
+        }
+        Rectangle {
+            x: 0
+            y: 25
+            width: 25
+            height: 25
+            color: "#00ff00"
+        }
+        Rectangle {
+            x: 25
+            y: 25
+            width: 25
+            height: 25
+            color: "#0000ff"
+        }
+    }
+    // ShaderEffectSource item. Mirroring should not affect how it looks.
+    ShaderEffectSource {
+        id: theSource
+        x: 150
+        y: 0
+        width: 50
+        height: 50
+        sourceItem: box2
+        textureMirroring: mirroring
+    }
+    // ShaderEffect item. Mirroring should affect how it looks.
+    ShaderEffect {
+        x: 200
+        y: 0
+        width: 50
+        height: 50
+        property variant source: theSource
+        fragmentShader: "
+            uniform lowp sampler2D source;
+            varying highp vec2 qt_TexCoord0;
+            void main() {
+                gl_FragColor = texture2D(source, qt_TexCoord0);
+            }"
+    }
+}