implement DrawLine with shader

data/shaders/drawline.frag

@@ -0,0 +1,20 @@
+#version 330
+
+uniform ivec2   uScreenSize;
+uniform ivec4   uClip;
+uniform vec4    uColour;
+
+in vec2 fPosition;
+
+layout (location = 0) out vec4 oColour;
+
+void main()
+{
+    if (fPosition.x < uClip.x || fPosition.x > uClip.z ||
+        fPosition.y < uClip.y || fPosition.y > uClip.w)
+    {
+        discard;
+    }
+
+    oColour = uColour;
+}

data/shaders/drawline.vert

@@ -0,0 +1,30 @@
+#version 330
+
+uniform ivec2 uScreenSize;
+uniform ivec4 uBounds;
+
+in int vIndex;
+
+out vec2 fPosition;
+
+void main()
+{
+    vec2 pos;
+    if (vIndex == 0)
+    {
+        pos = uBounds.xy;
+    }
+    else
+    {
+        pos = uBounds.zw;
+    }
+
+    fPosition = pos;
+
+    // Transform screen coordinates to viewport
+    pos.x = (pos.x * (2.0 / uScreenSize.x)) - 1.0;
+    pos.y = (pos.y * (2.0 / uScreenSize.y)) - 1.0;
+    pos.y *= -1;
+
+    gl_Position = vec4(pos, 0.0, 1.0);
+}

openrct2.vcxproj

@@ -22,6 +22,8 @@
     <None Include="data\shaders\drawimage.vert" />
     <None Include="data\shaders\drawimagemasked.frag" />
     <None Include="data\shaders\drawimagemasked.vert" />
+    <None Include="data\shaders\drawline.frag" />
+    <None Include="data\shaders\drawline.vert" />
     <None Include="data\shaders\fillrect.frag" />
     <None Include="data\shaders\fillrect.vert" />
     <None Include="openrct2.exe" />
@@ -53,6 +55,7 @@
     <ClCompile Include="src\drawing\engines\opengl\CopyFramebufferShader.cpp" />
     <ClCompile Include="src\drawing\engines\opengl\DrawImageMaskedShader.cpp" />
     <ClCompile Include="src\drawing\engines\opengl\DrawImageShader.cpp" />
+    <ClCompile Include="src\drawing\engines\opengl\DrawLineShader.cpp" />
     <ClCompile Include="src\drawing\engines\opengl\FillRectShader.cpp" />
     <ClCompile Include="src\drawing\engines\opengl\OpenGLAPI.cpp" />
     <ClCompile Include="src\drawing\engines\opengl\OpenGLDrawingEngine.cpp" />
@@ -356,6 +359,7 @@
     <ClInclude Include="src\drawing\engines\opengl\CopyFramebufferShader.h" />
     <ClInclude Include="src\drawing\engines\opengl\DrawImageMaskedShader.h" />
     <ClInclude Include="src\drawing\engines\opengl\DrawImageShader.h" />
+    <ClInclude Include="src\drawing\engines\opengl\DrawLineShader.h" />
     <ClInclude Include="src\drawing\engines\opengl\FillRectShader.h" />
     <ClInclude Include="src\drawing\engines\opengl\GLSLTypes.h" />
     <ClInclude Include="src\drawing\engines\opengl\OpenGLAPI.h" />

src/drawing/engines/opengl/DrawLineShader.cpp

@@ -0,0 +1,86 @@
+#pragma region Copyright (c) 2014-2016 OpenRCT2 Developers
+/*****************************************************************************
+ * OpenRCT2, an open source clone of Roller Coaster Tycoon 2.
+ *
+ * OpenRCT2 is the work of many authors, a full list can be found in contributors.md
+ * For more information, visit https://github.com/OpenRCT2/OpenRCT2
+ *
+ * OpenRCT2 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * A full copy of the GNU General Public License can be found in licence.txt
+ *****************************************************************************/
+#pragma endregion
+
+#ifndef DISABLE_OPENGL
+
+#include "DrawLineShader.h"
+#include "OpenGLFramebuffer.h"
+
+DrawLineShader::DrawLineShader() : OpenGLShaderProgram("drawline")
+{
+    GetLocations();
+
+    glGenBuffers(1, &_vbo);
+    glGenVertexArrays(1, &_vao);
+
+    vec2i vertices[] = { 0, 1 };
+    glBindBuffer(GL_ARRAY_BUFFER, _vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+    glBindVertexArray(_vao);
+    glEnableVertexAttribArray(vIndex);
+    glVertexAttribIPointer(vIndex, 1, GL_INT, 0, nullptr);
+
+    Use();
+}
+
+DrawLineShader::~DrawLineShader()
+{
+    glDeleteBuffers(1, &_vbo);
+    glDeleteVertexArrays(1, &_vao);
+
+    glBindVertexArray(_vao);
+}
+
+void DrawLineShader::GetLocations()
+{
+    uScreenSize = GetUniformLocation("uScreenSize");
+    uClip       = GetUniformLocation("uClip");
+    uBounds     = GetUniformLocation("uBounds");
+    uColour     = GetUniformLocation("uColour");
+
+    vIndex      = GetAttributeLocation("vIndex");
+}
+
+void DrawLineShader::SetScreenSize(sint32 width, sint32 height)
+{
+    glUniform2i(uScreenSize, width, height);
+}
+
+void DrawLineShader::SetClip(sint32 left, sint32 top, sint32 right, sint32 bottom)
+{
+    glUniform4i(uClip, left, top, right, bottom);
+}
+
+void DrawLineShader::SetBounds(sint32 x0, sint32 y0, sint32 x1, sint32 y1)
+{
+    glUniform4i(uBounds, x0, y0, x1, y1);
+}
+
+void DrawLineShader::SetColour(vec4f colour)
+{
+    glUniform4f(uColour, colour.r, colour.g, colour.b, colour.a);
+}
+
+void DrawLineShader::Draw(sint32 x0, sint32 y0, sint32 x1, sint32 y1)
+{
+    SetBounds(x0, y0, x1, y1);
+
+    glBindVertexArray(_vao);
+    glDrawArrays(GL_LINES, 0, 2);
+}
+
+#endif /* DISABLE_OPENGL */

src/drawing/engines/opengl/DrawLineShader.h

@@ -0,0 +1,48 @@
+#pragma region Copyright (c) 2014-2016 OpenRCT2 Developers
+/*****************************************************************************
+ * OpenRCT2, an open source clone of Roller Coaster Tycoon 2.
+ *
+ * OpenRCT2 is the work of many authors, a full list can be found in contributors.md
+ * For more information, visit https://github.com/OpenRCT2/OpenRCT2
+ *
+ * OpenRCT2 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * A full copy of the GNU General Public License can be found in licence.txt
+ *****************************************************************************/
+#pragma endregion
+
+#pragma once
+
+#include "GLSLTypes.h"
+#include "OpenGLShaderProgram.h"
+
+class DrawLineShader : public OpenGLShaderProgram
+{
+private:
+    GLuint uScreenSize;
+    GLuint uClip;
+    GLuint uBounds;
+    GLuint uColour;
+
+    GLuint vIndex;
+
+    GLuint _vbo;
+    GLuint _vao;
+
+public:
+    DrawLineShader();
+    ~DrawLineShader() override;
+
+    void SetScreenSize(sint32 width, sint32 height);
+    void SetClip(sint32 left, sint32 top, sint32 right, sint32 bottom);
+    void SetBounds(sint32 x0, sint32 y0, sint32 x1, sint32 y1);
+    void SetColour(vec4f colour);
+
+    void Draw(sint32 x0, sint32 y0, sint32 x1, sint32 y1);
+
+private:
+    void GetLocations();
+};

src/drawing/engines/opengl/OpenGLDrawingEngine.cpp

@@ -35,6 +35,7 @@ IDrawingEngine * DrawingEngineFactory::CreateOpenGL()
 #include "CopyFramebufferShader.h"
 #include "DrawImageShader.h"
 #include "DrawImageMaskedShader.h"
+#include "DrawLineShader.h"
 #include "FillRectShader.h"
 #include "SwapFramebuffer.h"
 
@@ -169,6 +170,7 @@ private:
 
     DrawImageShader *       _drawImageShader        = nullptr;
     DrawImageMaskedShader * _drawImageMaskedShader  = nullptr;
+    DrawLineShader *        _drawLineShader         = nullptr;
     FillRectShader *        _fillRectShader         = nullptr;
     GLuint _vbo;
 
@@ -464,6 +466,7 @@ OpenGLDrawingContext::~OpenGLDrawingContext()
 {
     delete _drawImageShader;
     delete _drawImageMaskedShader;
+    delete _drawLineShader;
     delete _fillRectShader;
 }
 
@@ -476,6 +479,7 @@ void OpenGLDrawingContext::Initialise()
 {
     _drawImageShader = new DrawImageShader();
     _drawImageMaskedShader = new DrawImageMaskedShader();
+    _drawLineShader = new DrawLineShader();
     _fillRectShader = new FillRectShader();
 }
 
@@ -530,14 +534,13 @@ void OpenGLDrawingContext::FillRect(uint32 colour, sint32 left, sint32 top, sint
 
 void OpenGLDrawingContext::DrawLine(uint32 colour, sint32 x1, sint32 y1, sint32 x2, sint32 y2)
 {
-    return;
-
     vec4f paletteColour = _engine->GLPalette[colour & 0xFF];
-    glColor3f(paletteColour.r, paletteColour.g, paletteColour.b);
-    glBegin(GL_LINES);
-        glVertex2i(x1, y1);
-        glVertex2i(x2, y2);
-    glEnd();
+
+    _drawLineShader->Use();
+    _drawLineShader->SetScreenSize(gScreenWidth, gScreenHeight);
+    _drawLineShader->SetClip(_clipLeft, _clipTop, _clipRight, _clipBottom);
+    _drawLineShader->SetColour(paletteColour);
+    _drawLineShader->Draw(x1, y1, x2, y2);
 }
 
 void OpenGLDrawingContext::DrawSprite(uint32 image, sint32 x, sint32 y, uint32 tertiaryColour)