Vertex shaders can write to gl_PointSize (fixes #1603).

If a shader uses gl_PointSize then it can only be used when drawing points. If a shader doesn't use gl_PointSize then it can't be used when drawing points.

Added 'ConstantPointSize' and 'CurrentDPIScale' built-in shader uniforms.

ConstantPointSize is in DPI-scaled points, whereas gl_PointSize is in pixels, so to get the correct default behaviour a shader needs to do gl_PointSize = ConstantPointSize * CurrentDPIScale

src/modules/graphics/opengl/Graphics.cpp

@@ -304,6 +304,9 @@ bool Graphics::setMode(int width, int height, int pixelwidth, int pixelheight, b
 		glEnable(GL_TEXTURE_2D);
 	}
 
+	if (!GLAD_ES_VERSION_2_0)
+		glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
+
 	gl.setTextureUnit(0);
 
 	// Set pixel row alignment - code that calls glTexSubImage and glReadPixels
@@ -1444,10 +1447,9 @@ void Graphics::setBlendState(const BlendState &blend)
 
 void Graphics::setPointSize(float size)
 {
-	if (batchedDrawState.primitiveMode == PRIMITIVE_POINTS)
+	if (size != states.back().pointSize)
 		flushBatchedDraws();
 
-	gl.setPointSize(size * getCurrentDPIScale());
 	states.back().pointSize = size;
 }
 

src/modules/graphics/opengl/OpenGL.cpp

@@ -943,19 +943,6 @@ void OpenGL::setScissor(const Rect &v, bool rtActive)
 	state.scissor = v;
 }
 
-void OpenGL::setPointSize(float size)
-{
-	if (GLAD_VERSION_1_0)
-		glPointSize(size);
-
-	state.pointSize = size;
-}
-
-float OpenGL::getPointSize() const
-{
-	return state.pointSize;
-}
-
 void OpenGL::setEnableState(EnableState enablestate, bool enable)
 {
 	GLenum glstate = GL_NONE;

src/modules/graphics/opengl/OpenGL.h

@@ -270,12 +270,6 @@ public:
 	 **/
 	void setScissor(const Rect &v, bool rtActive);
 
-	/**
-	 * Sets the global point size.
-	 **/
-	void setPointSize(float size);
-	float getPointSize() const;
-
 	/**
 	 * State-tracked version of glEnable.
 	 **/

src/modules/graphics/opengl/Shader.cpp

@@ -48,7 +48,6 @@ Shader::Shader(love::graphics::ShaderStage *vertex, love::graphics::ShaderStage
 	, builtinUniforms()
 	, builtinUniformInfo()
 	, builtinAttributes()
-	, lastPointSize(0.0f)
 {
 	// load shader source and create program object
 	loadVolatile();
@@ -430,8 +429,6 @@ bool Shader::loadVolatile()
 {
 	OpenGL::TempDebugGroup debuggroup("Shader load");
 
-	lastPointSize = -1.0f;
-
 	// zero out active texture list
 	textureUnits.clear();
 	textureUnits.push_back(TextureUnit());
@@ -971,26 +968,11 @@ void Shader::setVideoTextures(love::graphics::Texture *ytexture, love::graphics:
 	}
 }
 
-void Shader::updatePointSize(float size)
-{
-	if (size == lastPointSize || current != this)
-		return;
-
-	GLint location = builtinUniforms[BUILTIN_POINT_SIZE];
-	if (location >= 0)
-		glUniform1f(location, size);
-
-	lastPointSize = size;
-}
-
 void Shader::updateBuiltinUniforms(love::graphics::Graphics *gfx, int viewportW, int viewportH)
 {
 	if (current != this)
 		return;
 
-	if (GLAD_ES_VERSION_2_0)
-		updatePointSize(gl.getPointSize());
-
 	BuiltinUniformData data;
 
 	data.transformMatrix = gfx->getTransform();
@@ -1010,6 +992,12 @@ void Shader::updateBuiltinUniforms(love::graphics::Graphics *gfx, int viewportW,
 		}
 	}
 
+	// Store DPI scale in an unused component of another vector.
+	data.normalMatrix[0].w = (float) gfx->getCurrentDPIScale();
+
+	// Same with point size.
+	data.normalMatrix[1].w = gfx->getPointSize();
+
 	data.screenSizeParams.x = viewportW;
 	data.screenSizeParams.y = viewportH;
 

src/modules/graphics/opengl/Shader.h

@@ -43,10 +43,6 @@ class Shader final : public love::graphics::Shader, public Volatile
 {
 public:
 
-	/**
-	 * Creates a new Shader using a list of source codes.
-	 * Source must contain either vertex or pixel shader code, or both.
-	 **/
 	Shader(love::graphics::ShaderStage *vertex, love::graphics::ShaderStage *pixel);
 	virtual ~Shader();
 
@@ -67,7 +63,6 @@ public:
 	ptrdiff_t getHandle() const override;
 	void setVideoTextures(love::graphics::Texture *ytexture, love::graphics::Texture *cbtexture, love::graphics::Texture *crtexture) override;
 
-	void updatePointSize(float size);
 	void updateBuiltinUniforms(love::graphics::Graphics *gfx, int viewportW, int viewportH);
 
 private:
@@ -128,8 +123,6 @@ private:
 
 	std::vector<std::pair<const UniformInfo *, int>> pendingUniformUpdates;
 
-	float lastPointSize;
-
 }; // Shader
 
 } // opengl