From 77305d47c2bc45068427d6a501d312fbba4db026 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <slouken@libsdl.org>
Date: Sat, 1 Oct 2016 11:46:32 -0700
Subject: [PATCH] Fixed bug 3345 - SDL_RenderClear inconsistency with ClipRect

Simon Hug

The description of the SDL_RenderClear function in the SDL_render.h header says the following:

"This function clears the entire rendering target, ignoring the viewport."

The word "entire" implies that the clipping rectangle set with SDL_RenderSetClipRect also gets ignored. This is left somewhat ambiguous if only the viewport is mentioned. Minor thing, but let's see what the implementations actually do.

The software renderer ignores the clipping rectangle when clearing. It even has a comment on this: /* By definition the clear ignores the clip rect */

Most other render drivers (opengl, opengles, opengles2, direct3d, and psp [I assume. Can't test it.]) use the scissor test for the ClipRect and don't disable it when clearing. Clearing will only happen within the clipping rectangle for these drivers.

An exception is direct3d11 which uses a clear function that ignores the scissor test.
---
 include/SDL_render.h                    | 3 ++-
 src/render/direct3d/SDL_render_d3d.c    | 8 ++++++++
 src/render/opengl/SDL_render_gl.c       | 8 ++++++++
 src/render/opengles/SDL_render_gles.c   | 8 ++++++++
 src/render/opengles2/SDL_render_gles2.c | 8 ++++++++
 5 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/include/SDL_render.h b/include/SDL_render.h
index 6e3daf5228109..60c87b66ab63b 100644
--- a/include/SDL_render.h
+++ b/include/SDL_render.h
@@ -682,7 +682,8 @@ extern DECLSPEC int SDLCALL SDL_GetRenderDrawBlendMode(SDL_Renderer * renderer,
 /**
  *  \brief Clear the current rendering target with the drawing color
  *
- *  This function clears the entire rendering target, ignoring the viewport.
+ *  This function clears the entire rendering target, ignoring the viewport and
+ *  the clip rectangle.
  *
  *  \return 0 on success, or -1 on error
  */
diff --git a/src/render/direct3d/SDL_render_d3d.c b/src/render/direct3d/SDL_render_d3d.c
index da8c1af075377..c54897fe7ee34 100644
--- a/src/render/direct3d/SDL_render_d3d.c
+++ b/src/render/direct3d/SDL_render_d3d.c
@@ -1311,6 +1311,10 @@ D3D_RenderClear(SDL_Renderer * renderer)
         BackBufferHeight = data->pparams.BackBufferHeight;
     }
 
+    if (renderer->clipping_enabled) {
+        IDirect3DDevice9_SetRenderState(data->device, D3DRS_SCISSORTESTENABLE, FALSE);
+    }
+
     /* Don't reset the viewport if we don't have to! */
     if (!renderer->viewport.x && !renderer->viewport.y &&
         renderer->viewport.w == BackBufferWidth &&
@@ -1340,6 +1344,10 @@ D3D_RenderClear(SDL_Renderer * renderer)
         IDirect3DDevice9_SetViewport(data->device, &viewport);
     }
 
+    if (renderer->clipping_enabled) {
+        IDirect3DDevice9_SetRenderState(data->device, D3DRS_SCISSORTESTENABLE, TRUE);
+    }
+
     if (FAILED(result)) {
         return D3D_SetError("Clear()", result);
     }
diff --git a/src/render/opengl/SDL_render_gl.c b/src/render/opengl/SDL_render_gl.c
index 7c6f80d4493fc..0276f28da5fd8 100644
--- a/src/render/opengl/SDL_render_gl.c
+++ b/src/render/opengl/SDL_render_gl.c
@@ -1146,8 +1146,16 @@ GL_RenderClear(SDL_Renderer * renderer)
                        (GLfloat) renderer->b * inv255f,
                        (GLfloat) renderer->a * inv255f);
 
+    if (renderer->clipping_enabled) {
+        data->glDisable(GL_SCISSOR_TEST);
+    }
+
     data->glClear(GL_COLOR_BUFFER_BIT);
 
+    if (renderer->clipping_enabled) {
+        data->glEnable(GL_SCISSOR_TEST);
+    }
+
     return 0;
 }
 
diff --git a/src/render/opengles/SDL_render_gles.c b/src/render/opengles/SDL_render_gles.c
index b8b8c1d49d15a..56cbad680523e 100644
--- a/src/render/opengles/SDL_render_gles.c
+++ b/src/render/opengles/SDL_render_gles.c
@@ -815,9 +815,17 @@ GLES_RenderClear(SDL_Renderer * renderer)
                  (GLfloat) renderer->g * inv255f,
                  (GLfloat) renderer->b * inv255f,
                  (GLfloat) renderer->a * inv255f);
+    
+    if (renderer->clipping_enabled) {
+        data->glDisable(GL_SCISSOR_TEST);
+    }
 
     data->glClear(GL_COLOR_BUFFER_BIT);
 
+    if (renderer->clipping_enabled) {
+        data->glEnable(GL_SCISSOR_TEST);
+    }
+
     return 0;
 }
 
diff --git a/src/render/opengles2/SDL_render_gles2.c b/src/render/opengles2/SDL_render_gles2.c
index edefa641598dc..30d761ad7360f 100644
--- a/src/render/opengles2/SDL_render_gles2.c
+++ b/src/render/opengles2/SDL_render_gles2.c
@@ -1327,8 +1327,16 @@ GLES2_RenderClear(SDL_Renderer * renderer)
         data->clear_a = renderer->a;
     }
 
+    if (renderer->clipping_enabled) {
+        data->glDisable(GL_SCISSOR_TEST);
+    }
+
     data->glClear(GL_COLOR_BUFFER_BIT);
 
+    if (renderer->clipping_enabled) {
+        data->glEnable(GL_SCISSOR_TEST);
+    }
+
     return 0;
 }