1 files changed, 189 insertions, 0 deletions
diff --git a/vcl/opengl/LineRenderUtils.cxx b/vcl/opengl/LineRenderUtils.cxx
new file mode 100644
index 000000000..e130fb93b
--- /dev/null
+++ b/vcl/opengl/LineRenderUtils.cxx
@@ -0,0 +1,189 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ */
+
+#include <opengl/LineRenderUtils.hxx>
+#include <opengl/VertexUtils.hxx>
+
+namespace vcl
+{
+
+LineBuilder::LineBuilder(std::vector<Vertex>& rVertices, std::vector<GLuint>& rIndices,
+                Color nColor, GLfloat fTransparency,
+                GLfloat fLineWidth, bool bUseAA)
+    : mrVertices(rVertices)
+    , mrIndices(rIndices)
+    , mR(nColor.GetRed())
+    , mG(nColor.GetGreen())
+    , mB(nColor.GetBlue())
+    , mA((1.0f - fTransparency) * 255.0f)
+    , mfLineWidth(fLineWidth)
+    , mfLineWidthAndAA(bUseAA ? fLineWidth : -fLineWidth)
+    , mnInitialIndexSize(rIndices.size())
+    , mbIncomplete(false)
+{
+}
+
+void LineBuilder::appendLineSegment(const glm::vec2& rPoint1, const glm::vec2& rNormal1, GLfloat aExtrusion1,
+                                    const glm::vec2& rPoint2, const glm::vec2& rNormal2, GLfloat aExtrusion2)
+{
+    GLuint zero = mrVertices.size();
+
+    mrVertices.insert(mrVertices.end(), {
+        {rPoint1, glm::vec4{mR, mG, mB, mA}, glm::vec4{-rNormal1.x, -rNormal1.y, -aExtrusion1, mfLineWidthAndAA}},
+        {rPoint1, glm::vec4{mR, mG, mB, mA}, glm::vec4{ rNormal1.x,  rNormal1.y,  aExtrusion1, mfLineWidthAndAA}},
+        {rPoint2, glm::vec4{mR, mG, mB, mA}, glm::vec4{-rNormal2.x, -rNormal2.y, -aExtrusion2, mfLineWidthAndAA}},
+        {rPoint2, glm::vec4{mR, mG, mB, mA}, glm::vec4{ rNormal2.x,  rNormal2.y,  aExtrusion2, mfLineWidthAndAA}},
+    });
+
+    mrIndices.insert(mrIndices.end(), {
+        zero + 0, zero + 1, zero + 2,
+        zero + 2, zero + 1, zero + 3
+    });
+
+}
+
+void LineBuilder::appendLine(const glm::vec2& rPoint1, const glm::vec2& rPoint2)
+{
+    glm::vec2 aLineVector = vcl::vertex::normalize(rPoint2 - rPoint1);
+    glm::vec2 aNormal = vcl::vertex::perpendicular(aLineVector);
+
+    appendLineSegment(rPoint1, aNormal, 1.0f,
+                      rPoint2, aNormal, 1.0f);
+}
+
+void LineBuilder::appendAndConnectLinePoint(const glm::vec2& rPoint, const glm::vec2& aNormal, GLfloat aExtrusion)
+{
+    GLuint zero = mrVertices.size();
+
+    mrVertices.insert(mrVertices.end(), {
+        {rPoint, glm::vec4{mR, mG, mB, mA}, glm::vec4{-aNormal.x, -aNormal.y, -aExtrusion, mfLineWidthAndAA}},
+        {rPoint, glm::vec4{mR, mG, mB, mA}, glm::vec4{ aNormal.x,  aNormal.y,  aExtrusion, mfLineWidthAndAA}},
+    });
+
+    if (mnInitialIndexSize == mrIndices.size())
+    {
+        mrIndices.insert(mrIndices.end(), {
+            zero + 0, zero + 1
+        });
+        mbIncomplete = true;
+    }
+    else
+    {
+        if (mbIncomplete)
+        {
+            mrIndices.insert(mrIndices.end(), {
+                                    zero + 0,
+                zero + 0, zero - 1, zero + 1
+            });
+            mbIncomplete = false;
+        }
+        else
+        {
+            mrIndices.insert(mrIndices.end(), {
+                zero - 2, zero - 1, zero + 0,
+                zero + 0, zero - 1, zero + 1
+            });
+        }
+    }
+}
+
+void LineBuilder::appendMiterJoint(glm::vec2 const& point, const glm::vec2& prevLineVector,
+                                   glm::vec2 const& nextLineVector)
+{
+    // With miter join we calculate the extrusion vector by adding normals of
+    // previous and next line segment. The vector shows the way but we also
+    // need the length (otherwise the line will be deformed). Length factor is
+    // calculated as dot product of extrusion vector and one of the normals.
+    // The value we get is the inverse length (used in the shader):
+    // length = line_width / dot(extrusionVector, normal)
+
+    glm::vec2 normal(-prevLineVector.y, prevLineVector.x);
+
+    glm::vec2 tangent = vcl::vertex::normalize(nextLineVector + prevLineVector);
+    glm::vec2 extrusionVector(-tangent.y, tangent.x);
+    GLfloat length = glm::dot(extrusionVector, normal);
+
+    appendAndConnectLinePoint(point, extrusionVector, length);
+}
+
+void LineBuilder::appendBevelJoint(glm::vec2 const& point, const glm::vec2& prevLineVector,
+                                   const glm::vec2& nextLineVector)
+{
+    // For bevel join we just add 2 additional vertices and use previous
+    // line segment normal and next line segment normal as extrusion vector.
+    // All the magic is done by the fact that we draw triangle strips, so we
+    // cover the joins correctly.
+
+    glm::vec2 prevNormal(-prevLineVector.y, prevLineVector.x);
+    glm::vec2 nextNormal(-nextLineVector.y, nextLineVector.x);
+
+    appendAndConnectLinePoint(point, prevNormal, 1.0f);
+    appendAndConnectLinePoint(point, nextNormal, 1.0f);
+}
+
+void LineBuilder::appendRoundJoint(glm::vec2 const& point, const glm::vec2& prevLineVector,
+                                   const glm::vec2& nextLineVector)
+{
+    // For round join we do a similar thing as in bevel, we add more intermediate
+    // vertices and add normals to get extrusion vectors in the between the
+    // both normals.
+
+    // 3 additional extrusion vectors + normals are enough to make most
+    // line joins look round. Ideally the number of vectors could be
+    // calculated.
+
+    glm::vec2 prevNormal(-prevLineVector.y, prevLineVector.x);
+    glm::vec2 nextNormal(-nextLineVector.y, nextLineVector.x);
+
+    glm::vec2 middle = vcl::vertex::normalize(prevNormal + nextNormal);
+    glm::vec2 middleLeft  = vcl::vertex::normalize(prevNormal + middle);
+    glm::vec2 middleRight = vcl::vertex::normalize(middle + nextNormal);
+
+    appendAndConnectLinePoint(point, prevNormal, 1.0f);
+    appendAndConnectLinePoint(point, middleLeft, 1.0f);
+    appendAndConnectLinePoint(point, middle, 1.0f);
+    appendAndConnectLinePoint(point, middleRight, 1.0f);
+    appendAndConnectLinePoint(point, nextNormal, 1.0f);
+}
+
+void LineBuilder::appendRoundLineCapVertices(const glm::vec2& rPoint1, const glm::vec2& rPoint2)
+{
+    constexpr int nRoundCapIteration = 12;
+
+    glm::vec2 lineVector = vcl::vertex::normalize(rPoint2 - rPoint1);
+    glm::vec2 normal(-lineVector.y, lineVector.x);
+    glm::vec2 previousRoundNormal = normal;
+
+    for (int nFactor = 1; nFactor <= nRoundCapIteration; nFactor++)
+    {
+        float angle = float(nFactor) * (M_PI / float(nRoundCapIteration));
+        glm::vec2 roundNormal(normal.x * glm::cos(angle) - normal.y * glm::sin(angle),
+                              normal.x * glm::sin(angle) + normal.y * glm::cos(angle));
+
+        appendLineSegment(rPoint1, previousRoundNormal, 1.0f,
+                          rPoint1, roundNormal, 1.0f);
+        previousRoundNormal = roundNormal;
+    }
+}
+
+void LineBuilder::appendSquareLineCapVertices(const glm::vec2& rPoint1, const glm::vec2& rPoint2)
+{
+    glm::vec2 lineVector = vcl::vertex::normalize(rPoint2 - rPoint1);
+    glm::vec2 normal(-lineVector.y, lineVector.x);
+
+    glm::vec2 extrudedPoint = rPoint1 + -lineVector * (mfLineWidth / 2.0f);
+
+    appendLineSegment(extrudedPoint, normal, 1.0f,
+                      rPoint1,       normal, 1.0f);
+}
+
+} // end vcl
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */