Add basic ortho and perspective projection APIs to love.graphics.

- Added love.graphics.setOrthoProjection.
- Added love.graphics.setPerspectiveProjection.
- Added love.graphics.resetProjection.

Note that the projection is reset whenever the canvas changes.

src/modules/graphics/opengl/Graphics.cpp

@@ -165,6 +165,18 @@ love::graphics::Buffer *Graphics::newBuffer(const Buffer::Settings &settings, co
 	return new Buffer(this, settings, format, data, size, arraylength);
 }
 
+Matrix4 Graphics::computeDeviceProjection(const Matrix4 &projection, bool rendertotexture) const
+{
+	uint32 flags = DEVICE_PROJECTION_DEFAULT;
+
+	// The projection matrix is flipped compared to rendering to a texture, due
+	// to OpenGL considering (0,0) bottom-left instead of top-left.
+	if (!rendertotexture)
+		flags |= DEVICE_PROJECTION_FLIP_Y;
+
+	return calculateDeviceProjection(projection, flags);
+}
+
 void Graphics::setViewportSize(int width, int height, int pixelwidth, int pixelheight)
 {
 	this->width = width;
@@ -182,8 +194,7 @@ void Graphics::setViewportSize(int width, int height, int pixelwidth, int pixelh
 		if (states.back().scissor)
 			setScissor(states.back().scissorRect);
 
-		// Set up the projection matrix
-		projectionMatrix = Matrix4::ortho(0.0, (float) width, (float) height, 0.0, -10.0f, 10.0f);
+		resetProjection();
 	}
 
 	updateBackbuffer(width, height, pixelwidth, pixelheight, requestedBackbufferMSAA);
@@ -719,7 +730,7 @@ void Graphics::setDebug(bool enable)
 	::printf("OpenGL debug output enabled (LOVE_GRAPHICS_DEBUG=1)\n");
 }
 
-void Graphics::setRenderTargetsInternal(const RenderTargets &rts, int w, int h, int pixelw, int pixelh, bool hasSRGBtexture)
+void Graphics::setRenderTargetsInternal(const RenderTargets &rts, int /*w*/, int /*h*/, int pixelw, int pixelh, bool hasSRGBtexture)
 {
 	const DisplayState &state = states.back();
 
@@ -734,19 +745,14 @@ void Graphics::setRenderTargetsInternal(const RenderTargets &rts, int w, int h,
 	if (iswindow)
 	{
 		gl.bindFramebuffer(OpenGL::FRAMEBUFFER_ALL, getInternalBackbufferFBO());
-
-		// The projection matrix is flipped compared to rendering to a texture,
-		// due to OpenGL considering (0,0) bottom-left instead of top-left.
-		projectionMatrix = Matrix4::ortho(0.0, (float) w, (float) h, 0.0, -10.0f, 10.0f);
 	}
 	else
 	{
 		bindCachedFBO(rts);
 
-		projectionMatrix = Matrix4::ortho(0.0, (float) w, 0.0, (float) h, -10.0f, 10.0f);
-
 		// Flip front face winding when rendering to a texture, since our
 		// projection matrix is flipped.
+		// Note: projection matrix is set at a higher level.
 		vertexwinding = vertexwinding == WINDING_CW ? WINDING_CCW : WINDING_CW;
 	}
 

src/modules/graphics/opengl/Graphics.h

@@ -62,6 +62,8 @@ public:
 	love::graphics::Texture *newTexture(const Texture::Settings &settings, const Texture::Slices *data = nullptr) override;
 	love::graphics::Buffer *newBuffer(const Buffer::Settings &settings, const std::vector<Buffer::DataDeclaration> &format, const void *data, size_t size, size_t arraylength) override;
 
+	Matrix4 computeDeviceProjection(const Matrix4 &projection, bool rendertotexture) const override;
+
 	void setViewportSize(int width, int height, int pixelwidth, int pixelheight) override;
 	bool setMode(int width, int height, int pixelwidth, int pixelheight, bool windowhasstencil, int msaa) override;
 	void unSetMode() override;

src/modules/graphics/opengl/Shader.cpp

@@ -1081,7 +1081,7 @@ void Shader::updateBuiltinUniforms(love::graphics::Graphics *gfx, int viewportW,
 	BuiltinUniformData data;
 
 	data.transformMatrix = gfx->getTransform();
-	data.projectionMatrix = gfx->getProjection();
+	data.projectionMatrix = gfx->getDeviceProjection();
 
 	// The normal matrix is the transpose of the inverse of the rotation portion
 	// (top-left 3x3) of the transform matrix.