From 0c8a47b5af871211fae15cee04b96c4be44dbdd4 Mon Sep 17 00:00:00 2001
From: Paul Chote <pchote@users.noreply.github.com>
Date: Sun, 3 Nov 2019 17:25:41 +0000
Subject: [PATCH] Add scissor support to IFrameBuffer.

---
 OpenRA.Game/Graphics/PlatformInterfaces.cs    |  2 ++
 OpenRA.Platforms.Default/FrameBuffer.cs       | 23 +++++++++++++++++++
 .../ThreadedGraphicsContext.cs                | 15 ++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/OpenRA.Game/Graphics/PlatformInterfaces.cs b/OpenRA.Game/Graphics/PlatformInterfaces.cs
index a1e941f678..0dd6db0fce 100644
--- a/OpenRA.Game/Graphics/PlatformInterfaces.cs
+++ b/OpenRA.Game/Graphics/PlatformInterfaces.cs
@@ -111,6 +111,8 @@ namespace OpenRA
 	{
 		void Bind();
 		void Unbind();
+		void EnableScissor(Rectangle rect);
+		void DisableScissor();
 		ITexture Texture { get; }
 	}
 
diff --git a/OpenRA.Platforms.Default/FrameBuffer.cs b/OpenRA.Platforms.Default/FrameBuffer.cs
index 4388701953..224c4dd9d7 100644
--- a/OpenRA.Platforms.Default/FrameBuffer.cs
+++ b/OpenRA.Platforms.Default/FrameBuffer.cs
@@ -23,6 +23,7 @@ namespace OpenRA.Platforms.Default
 		readonly Color clearColor;
 		uint framebuffer, depth;
 		bool disposed;
+		bool scissored;
 
 		public FrameBuffer(Size size, ITextureInternal texture, Color clearColor)
 		{
@@ -100,6 +101,9 @@ namespace OpenRA.Platforms.Default
 
 		public void Unbind()
 		{
+			if (scissored)
+				throw new InvalidOperationException("Attempting to unbind FrameBuffer with an active scissor region.");
+
 			VerifyThreadAffinity();
 			OpenGL.glFlush();
 			OpenGL.CheckGLError();
@@ -109,6 +113,25 @@ namespace OpenRA.Platforms.Default
 			OpenGL.CheckGLError();
 		}
 
+		public void EnableScissor(Rectangle rect)
+		{
+			VerifyThreadAffinity();
+
+			OpenGL.glScissor(rect.X, rect.Y, Math.Max(rect.Width, 0), Math.Max(rect.Height, 0));
+			OpenGL.CheckGLError();
+			OpenGL.glEnable(OpenGL.GL_SCISSOR_TEST);
+			OpenGL.CheckGLError();
+			scissored = true;
+		}
+
+		public void DisableScissor()
+		{
+			VerifyThreadAffinity();
+			OpenGL.glDisable(OpenGL.GL_SCISSOR_TEST);
+			OpenGL.CheckGLError();
+			scissored = false;
+		}
+
 		public ITexture Texture
 		{
 			get
diff --git a/OpenRA.Platforms.Default/ThreadedGraphicsContext.cs b/OpenRA.Platforms.Default/ThreadedGraphicsContext.cs
index f4fae71f93..da6aee2fa1 100644
--- a/OpenRA.Platforms.Default/ThreadedGraphicsContext.cs
+++ b/OpenRA.Platforms.Default/ThreadedGraphicsContext.cs
@@ -454,6 +454,8 @@ namespace OpenRA.Platforms.Default
 		readonly Action bind;
 		readonly Action unbind;
 		readonly Action dispose;
+		readonly Action<object> enableScissor;
+		readonly Action disableScissor;
 
 		public ThreadedFrameBuffer(ThreadedGraphicsContext device, IFrameBuffer frameBuffer)
 		{
@@ -462,6 +464,9 @@ namespace OpenRA.Platforms.Default
 			bind = frameBuffer.Bind;
 			unbind = frameBuffer.Unbind;
 			dispose = frameBuffer.Dispose;
+
+			enableScissor = rect => frameBuffer.EnableScissor((Rectangle)rect);
+			disableScissor = frameBuffer.DisableScissor;
 		}
 
 		public ITexture Texture
@@ -482,6 +487,16 @@ namespace OpenRA.Platforms.Default
 			device.Post(unbind);
 		}
 
+		public void EnableScissor(Rectangle rect)
+		{
+			device.Post(enableScissor, rect);
+		}
+
+		public void DisableScissor()
+		{
+			device.Post(disableScissor);
+		}
+
 		public void Dispose()
 		{
 			device.Post(dispose);