From c1ddd97c87c729c7d05c7a74f82d41cfc5bd9cf8 Mon Sep 17 00:00:00 2001

From: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

Date: Tue, 12 Oct 2021 13:13:01 +0200

Subject: [PATCH 34/36] Fix distorted text with subpixel matrix translation

We would pixel-align native text *before* applying the

model-view matrix, which would cause GL_NEAREST artifacts to

show up when the text was positioned at a subpixel offset in

some cases. Instead, we pixel-align the coordinates after mapping

them to the view frustum, but before applying the projection to the

screen.

To make it easier to modify the buffer layout for the shaders the

next time, this also adds some constants for offsets.

[ChangeLog][Text] Fixed an issue where text using NativeRendering

would look slightly skewed if it was inside a parent that had

been positioned at a subpixel offset.

Pick-to: 5.15 6.2

Fixes: QTBUG-96112

Fixes: QTBUG-83626

Task-number: QTBUG-55638

Change-Id: Ifb785ad5830093df94afc75a7bc288e24ca7aa38

Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

(cherry picked from commit b21948f5e811ce1b7abf065bc48af61a231e86f4)

---

 .../scenegraph/qsgdefaultglyphnode_p.cpp      | 46 ++++++----

 .../scenegraph/shaders_ng/24bittextmask.frag  |  5 +-

 .../scenegraph/shaders_ng/32bitcolortext.frag |  5 +-

 .../scenegraph/shaders_ng/8bittextmask.frag   |  3 +-

 .../scenegraph/shaders_ng/8bittextmask_a.frag |  3 +-

 .../scenegraph/shaders_ng/outlinedtext.frag   |  5 +-

 .../scenegraph/shaders_ng/outlinedtext.vert   |  9 +-

 .../scenegraph/shaders_ng/outlinedtext_a.frag |  5 +-

 .../scenegraph/shaders_ng/styledtext.frag     |  3 +-

 .../scenegraph/shaders_ng/styledtext.vert     |  7 +-

 .../scenegraph/shaders_ng/styledtext_a.frag   |  3 +-

 src/quick/scenegraph/shaders_ng/textmask.frag |  3 +-

 src/quick/scenegraph/shaders_ng/textmask.vert |  7 +-

 ...text_nativerendering_subpixelpositions.qml | 91 +++++++++++++++++++

 14 files changed, 155 insertions(+), 40 deletions(-)

 create mode 100644 tests/manual/scenegraph_lancelot/data/text/text_nativerendering_subpixelpositions.qml

diff --git a/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp b/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp

index 3c60f830de..0fd6581dc4 100644

--- a/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp

+++ b/src/quick/scenegraph/qsgdefaultglyphnode_p.cpp

@@ -428,6 +428,18 @@ QSGTextMaskRhiShader::QSGTextMaskRhiShader(QFontEngine::GlyphFormat glyphFormat)

                       QStringLiteral(":/qt-project.org/scenegraph/shaders_ng/textmask.frag.qsb"));

 }

+enum UbufOffset {

+    ModelViewMatrixOffset = 0,

+    ProjectionMatrixOffset = ModelViewMatrixOffset + 64,

+    ColorOffset = ProjectionMatrixOffset + 64,

+    TextureScaleOffset = ColorOffset + 16,

+    DprOffset = TextureScaleOffset + 8,

+

+    // + 1 float padding (vec4 must be aligned to 16)

+    StyleColorOffset = DprOffset + 4 + 4,

+    ShiftOffset = StyleColorOffset + 16

+};

+

 bool QSGTextMaskRhiShader::updateUniformData(RenderState &state,

                                              QSGMaterial *newMaterial, QSGMaterial *oldMaterial)

 {

@@ -443,11 +455,14 @@ bool QSGTextMaskRhiShader::updateUniformData(RenderState &state,

     bool changed = false;

     QByteArray *buf = state.uniformData();

-    Q_ASSERT(buf->size() >= 92);

+    Q_ASSERT(buf->size() >= DprOffset + 4);

     if (state.isMatrixDirty()) {

-        const QMatrix4x4 m = state.combinedMatrix();

-        memcpy(buf->data(), m.constData(), 64);

+        const QMatrix4x4 mv = state.modelViewMatrix();

+        memcpy(buf->data() + ModelViewMatrixOffset, mv.constData(), 64);

+        const QMatrix4x4 p = state.projectionMatrix();

+        memcpy(buf->data() + ProjectionMatrixOffset, p.constData(), 64);

+

         changed = true;

     }

@@ -456,13 +471,13 @@ bool QSGTextMaskRhiShader::updateUniformData(RenderState &state,

     if (updated || !oldMat || oldRtex != newRtex) {

         const QVector2D textureScale = QVector2D(1.0f / mat->rhiGlyphCache()->width(),

                                                  1.0f / mat->rhiGlyphCache()->height());

-        memcpy(buf->data() + 64 + 16, &textureScale, 8);

+        memcpy(buf->data() + TextureScaleOffset, &textureScale, 8);

         changed = true;

     }

     if (!oldMat) {

         float dpr = state.devicePixelRatio();

-        memcpy(buf->data() + 64 + 16 + 8, &dpr, 4);

+        memcpy(buf->data() + DprOffset, &dpr, 4);

     }

     // move texture uploads/copies onto the renderer's soon-to-be-committed list

@@ -510,11 +525,11 @@ bool QSG8BitTextMaskRhiShader::updateUniformData(RenderState &state,

     QSGTextMaskMaterial *oldMat = static_cast<QSGTextMaskMaterial *>(oldMaterial);

     QByteArray *buf = state.uniformData();

-    Q_ASSERT(buf->size() >= 80);

+    Q_ASSERT(buf->size() >= ColorOffset + 16);

     if (oldMat == nullptr || mat->color() != oldMat->color() || state.isOpacityDirty()) {

         const QVector4D color = qsg_premultiply(mat->color(), state.opacity());

-        memcpy(buf->data() + 64, &color, 16);

+        memcpy(buf->data() + ColorOffset, &color, 16);

         changed = true;

     }

@@ -553,12 +568,12 @@ bool QSG24BitTextMaskRhiShader::updateUniformData(RenderState &state,

     QSGTextMaskMaterial *oldMat = static_cast<QSGTextMaskMaterial *>(oldMaterial);

     QByteArray *buf = state.uniformData();

-    Q_ASSERT(buf->size() >= 92);

+    Q_ASSERT(buf->size() >= ColorOffset + 16);

     if (oldMat == nullptr || mat->color() != oldMat->color() || state.isOpacityDirty()) {

         // shader takes vec4 but uses alpha only; coloring happens via the blend constant

         const QVector4D color = qsg_premultiply(mat->color(), state.opacity());

-        memcpy(buf->data() + 64, &color, 16);

+        memcpy(buf->data() + ColorOffset, &color, 16);

         changed = true;

     }

@@ -608,12 +623,12 @@ bool QSG32BitColorTextRhiShader::updateUniformData(RenderState &state,

     QSGTextMaskMaterial *oldMat = static_cast<QSGTextMaskMaterial *>(oldMaterial);

     QByteArray *buf = state.uniformData();

-    Q_ASSERT(buf->size() >= 92);

+    Q_ASSERT(buf->size() >= ColorOffset + 16);

     if (oldMat == nullptr || mat->color() != oldMat->color() || state.isOpacityDirty()) {

         // shader takes vec4 but uses alpha only

         const QVector4D color(0, 0, 0, mat->color().w() * state.opacity());

-        memcpy(buf->data() + 64, &color, 16);

+        memcpy(buf->data() + ColorOffset, &color, 16);

         changed = true;

     }

@@ -649,20 +664,17 @@ bool QSGStyledTextRhiShader::updateUniformData(RenderState &state,

     QSGStyledTextMaterial *oldMat = static_cast<QSGStyledTextMaterial *>(oldMaterial);

     QByteArray *buf = state.uniformData();

-    Q_ASSERT(buf->size() >= 120);

-

-    // matrix..dpr + 1 float padding (vec4 must be aligned to 16)

-    const int startOffset = 64 + 16 + 8 + 4 + 4;

+    Q_ASSERT(buf->size() >= ShiftOffset + 8);

     if (oldMat == nullptr || mat->styleColor() != oldMat->styleColor() || state.isOpacityDirty()) {

         const QVector4D styleColor = qsg_premultiply(mat->styleColor(), state.opacity());

-        memcpy(buf->data() + startOffset, &styleColor, 16);

+        memcpy(buf->data() + StyleColorOffset, &styleColor, 16);

         changed = true;

     }

     if (oldMat == nullptr || oldMat->styleShift() != mat->styleShift()) {

         const QVector2D v = mat->styleShift();

-        memcpy(buf->data() + startOffset + 16, &v, 8);

+        memcpy(buf->data() + ShiftOffset, &v, 8);

         changed = true;

     }

diff --git a/src/quick/scenegraph/shaders_ng/24bittextmask.frag b/src/quick/scenegraph/shaders_ng/24bittextmask.frag

index bc3826a924..ed8da4cd30 100644

--- a/src/quick/scenegraph/shaders_ng/24bittextmask.frag

+++ b/src/quick/scenegraph/shaders_ng/24bittextmask.frag

@@ -6,8 +6,9 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

-    vec4 color; // only alpha is used, but must be vec4 due to layout compat

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

+    vec4 color;

     vec2 textureScale;

     float dpr;

 } ubuf;

diff --git a/src/quick/scenegraph/shaders_ng/32bitcolortext.frag b/src/quick/scenegraph/shaders_ng/32bitcolortext.frag

index 63e445f90b..4198a4d339 100644

--- a/src/quick/scenegraph/shaders_ng/32bitcolortext.frag

+++ b/src/quick/scenegraph/shaders_ng/32bitcolortext.frag

@@ -6,8 +6,9 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

-    vec4 color; // only alpha is used, but must be vec4 due to layout compat

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

+    vec4 color;

     vec2 textureScale;

     float dpr;

 } ubuf;

diff --git a/src/quick/scenegraph/shaders_ng/8bittextmask.frag b/src/quick/scenegraph/shaders_ng/8bittextmask.frag

index 6304e821ff..a06743876d 100644

--- a/src/quick/scenegraph/shaders_ng/8bittextmask.frag

+++ b/src/quick/scenegraph/shaders_ng/8bittextmask.frag

@@ -6,7 +6,8 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

diff --git a/src/quick/scenegraph/shaders_ng/8bittextmask_a.frag b/src/quick/scenegraph/shaders_ng/8bittextmask_a.frag

index 0d0fa1cd3a..f725cbc5e7 100644

--- a/src/quick/scenegraph/shaders_ng/8bittextmask_a.frag

+++ b/src/quick/scenegraph/shaders_ng/8bittextmask_a.frag

@@ -6,7 +6,8 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

diff --git a/src/quick/scenegraph/shaders_ng/outlinedtext.frag b/src/quick/scenegraph/shaders_ng/outlinedtext.frag

index 947d161a50..e2f82d3845 100644

--- a/src/quick/scenegraph/shaders_ng/outlinedtext.frag

+++ b/src/quick/scenegraph/shaders_ng/outlinedtext.frag

@@ -11,11 +11,12 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    // must match styledtext

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

+    // the above must stay compatible with textmask/8bittextmask

     vec4 styleColor;

     vec2 shift;

 } ubuf;

diff --git a/src/quick/scenegraph/shaders_ng/outlinedtext.vert b/src/quick/scenegraph/shaders_ng/outlinedtext.vert

index 023f9dfdc2..4068e42f28 100644

--- a/src/quick/scenegraph/shaders_ng/outlinedtext.vert

+++ b/src/quick/scenegraph/shaders_ng/outlinedtext.vert

@@ -10,11 +10,12 @@ layout(location = 3) out vec2 sCoordLeft;

 layout(location = 4) out vec2 sCoordRight;

 layout(std140, binding = 0) uniform buf {

-    // must match styledtext

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

+    // the above must stay compatible with textmask/8bittextmask

     vec4 styleColor;

     vec2 shift;

 } ubuf;

@@ -28,6 +29,6 @@ void main()

      sCoordDown = (tCoord - vec2(0.0, 1.0)) * ubuf.textureScale;

      sCoordLeft = (tCoord - vec2(-1.0, 0.0)) * ubuf.textureScale;

      sCoordRight = (tCoord - vec2(1.0, 0.0)) * ubuf.textureScale;

-     vec3 dprSnapPos = floor(vCoord.xyz * ubuf.dpr + 0.5) / ubuf.dpr;

-     gl_Position = ubuf.matrix * vec4(dprSnapPos, vCoord.w);

+     vec4 xformed = ubuf.modelViewMatrix * vCoord;

+     gl_Position = ubuf.projectionMatrix * vec4(floor(xformed.xyz * ubuf.dpr + 0.5) / ubuf.dpr, xformed.w);

 }

diff --git a/src/quick/scenegraph/shaders_ng/outlinedtext_a.frag b/src/quick/scenegraph/shaders_ng/outlinedtext_a.frag

index 5b7bd9ca82..274d891a3c 100644

--- a/src/quick/scenegraph/shaders_ng/outlinedtext_a.frag

+++ b/src/quick/scenegraph/shaders_ng/outlinedtext_a.frag

@@ -11,11 +11,12 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    // must match styledtext

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

+    // the above must stay compatible with textmask/8bittextmask

     vec4 styleColor;

     vec2 shift;

 } ubuf;

diff --git a/src/quick/scenegraph/shaders_ng/styledtext.frag b/src/quick/scenegraph/shaders_ng/styledtext.frag

index 0b16396037..2e380dfeae 100644

--- a/src/quick/scenegraph/shaders_ng/styledtext.frag

+++ b/src/quick/scenegraph/shaders_ng/styledtext.frag

@@ -8,7 +8,8 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

diff --git a/src/quick/scenegraph/shaders_ng/styledtext.vert b/src/quick/scenegraph/shaders_ng/styledtext.vert

index beadf07c79..271dae8d8a 100644

--- a/src/quick/scenegraph/shaders_ng/styledtext.vert

+++ b/src/quick/scenegraph/shaders_ng/styledtext.vert

@@ -7,7 +7,8 @@ layout(location = 0) out vec2 sampleCoord;

 layout(location = 1) out vec2 shiftedSampleCoord;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

@@ -22,6 +23,6 @@ void main()

 {

      sampleCoord = tCoord * ubuf.textureScale;

      shiftedSampleCoord = (tCoord - ubuf.shift) * ubuf.textureScale;

-     vec3 dprSnapPos = floor(vCoord.xyz * ubuf.dpr + 0.5) / ubuf.dpr;

-     gl_Position = ubuf.matrix * vec4(dprSnapPos, vCoord.w);

+     vec4 xformed = ubuf.modelViewMatrix * vCoord;

+     gl_Position = ubuf.projectionMatrix * vec4(floor(xformed.xyz * ubuf.dpr + 0.5) / ubuf.dpr, xformed.w);

 }

diff --git a/src/quick/scenegraph/shaders_ng/styledtext_a.frag b/src/quick/scenegraph/shaders_ng/styledtext_a.frag

index b673137895..62e162c851 100644

--- a/src/quick/scenegraph/shaders_ng/styledtext_a.frag

+++ b/src/quick/scenegraph/shaders_ng/styledtext_a.frag

@@ -8,7 +8,8 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

diff --git a/src/quick/scenegraph/shaders_ng/textmask.frag b/src/quick/scenegraph/shaders_ng/textmask.frag

index 518d5c965f..ed8da4cd30 100644

--- a/src/quick/scenegraph/shaders_ng/textmask.frag

+++ b/src/quick/scenegraph/shaders_ng/textmask.frag

@@ -6,7 +6,8 @@ layout(location = 0) out vec4 fragColor;

 layout(binding = 1) uniform sampler2D _qt_texture;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

diff --git a/src/quick/scenegraph/shaders_ng/textmask.vert b/src/quick/scenegraph/shaders_ng/textmask.vert

index 9d80d5dadb..e0b3c01bce 100644

--- a/src/quick/scenegraph/shaders_ng/textmask.vert

+++ b/src/quick/scenegraph/shaders_ng/textmask.vert

@@ -6,7 +6,8 @@ layout(location = 1) in vec2 tCoord;

 layout(location = 0) out vec2 sampleCoord;

 layout(std140, binding = 0) uniform buf {

-    mat4 matrix;

+    mat4 modelViewMatrix;

+    mat4 projectionMatrix;

     vec4 color;

     vec2 textureScale;

     float dpr;

@@ -17,6 +18,6 @@ out gl_PerVertex { vec4 gl_Position; };

 void main()

 {

      sampleCoord = tCoord * ubuf.textureScale;

-     vec3 dprSnapPos = floor(vCoord.xyz * ubuf.dpr + 0.5) / ubuf.dpr;

-     gl_Position = ubuf.matrix * vec4(dprSnapPos, vCoord.w);

+     vec4 xformed = ubuf.modelViewMatrix * vCoord;

+     gl_Position = ubuf.projectionMatrix * vec4(floor(xformed.xyz * ubuf.dpr + 0.5) / ubuf.dpr, xformed.w);

 }

diff --git a/tests/manual/scenegraph_lancelot/data/text/text_nativerendering_subpixelpositions.qml b/tests/manual/scenegraph_lancelot/data/text/text_nativerendering_subpixelpositions.qml

new file mode 100644

index 0000000000..c60fc4d8b0

--- /dev/null

+++ b/tests/manual/scenegraph_lancelot/data/text/text_nativerendering_subpixelpositions.qml

@@ -0,0 +1,91 @@

+import QtQuick 2.0

+

+//vary font style, native rendering at non-integer offsets

+

+Item {

+    id: topLevel

+    width: 320

+    height: 580

+

+    Repeater {

+        model: [Text.Normal, Text.Outline, Text.Raised, Text.Sunken]

+        Text {

+            y: 20 * index

+            clip: true

+            renderType: Text.NativeRendering

+            width: parent.width

+            wrapMode: Text.Wrap

+            font.pointSize: 10

+            style: modelData

+            styleColor: "green"

+            text: "The quick fox jumps in style " + modelData

+        }

+    }

+

+    Repeater {

+        model: [Text.Normal, Text.Outline, Text.Raised, Text.Sunken]

+        Text {

+            y: 100.5 + 20 * index

+            clip: true

+            renderType: Text.NativeRendering

+            width: parent.width

+            wrapMode: Text.Wrap

+            font.pointSize: 10

+            style: modelData

+            styleColor: "green"

+            text: "The quick fox jumps in style " + modelData

+        }

+    }

+

+    Repeater {

+        model: [Text.Normal, Text.Outline, Text.Raised, Text.Sunken]

+        Text {

+            y: 200.5 + 20 * index

+            x: 0.5

+            clip: true

+            renderType: Text.NativeRendering

+            width: parent.width

+            wrapMode: Text.Wrap

+            font.pointSize: 10

+            style: modelData

+            styleColor: "green"

+            text: "The quick fox jumps in style " + modelData

+        }

+    }

+

+    Repeater {

+        model: [Text.Normal, Text.Outline, Text.Raised, Text.Sunken]

+        Text {

+            y: 300.5 + 20 * index

+            x: 0.5

+            clip: true

+            renderType: Text.NativeRendering

+            width: parent.width

+            wrapMode: Text.Wrap

+            font.pointSize: 10

+            style: modelData

+            styleColor: "green"

+            text: "The quick fox jumps in style " + modelData

+        }

+    }

+

+    Repeater {

+        model: [Text.Normal, Text.Outline, Text.Raised, Text.Sunken]

+        Rectangle {

+            y: 400.5 + 20 * index

+            x: 0.5

+            width: topLevel.width

+            height: topLevel.height

+            clip: true

+            Text {

+                renderType: Text.NativeRendering

+                width: parent.width

+                wrapMode: Text.Wrap

+                font.pointSize: 10

+                style: modelData

+                styleColor: "green"

+                text: "The quick fox jumps in style " + modelData

+            }

+        }

+    }

+}

-- 

2.31.1