From 167cf14c1fc19b921f03101ef4df433ce09fab00 Mon Sep 17 00:00:00 2001
From: Ethan Lee <flibitijibibo@flibitijibibo.com>
Date: Tue, 5 Jan 2016 16:39:18 -0500
Subject: [PATCH] SDL_RenderSetIntegerScale

---
 include/SDL_render.h       | 24 ++++++++++++++++++++++++
 src/render/SDL_render.c    | 32 +++++++++++++++++++++++++++++++-
 src/render/SDL_sysrender.h |  3 +++
 3 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/include/SDL_render.h b/include/SDL_render.h
index e4ed2af6934e3..6e3daf5228109 100644
--- a/include/SDL_render.h
+++ b/include/SDL_render.h
@@ -499,6 +499,30 @@ extern DECLSPEC int SDLCALL SDL_RenderSetLogicalSize(SDL_Renderer * renderer, in
  */
 extern DECLSPEC void SDLCALL SDL_RenderGetLogicalSize(SDL_Renderer * renderer, int *w, int *h);
 
+/**
+ *  \brief Set whether to force integer scales for resolution-independent rendering
+ *
+ *  \param renderer The renderer for which integer scaling should be set.
+ *  \param enable   Enable or disable integer scaling
+ *
+ *  This function restricts the logical viewport to integer values - that is, when
+ *  a resolution is between two multiples of a logical size, the viewport size is
+ *  rounded down to the lower multiple.
+ *
+ *  \sa SDL_RenderSetLogicalSize()
+ */
+extern DECLSPEC int SDLCALL SDL_RenderSetIntegerScale(SDL_Renderer * renderer,
+                                                      SDL_bool enable);
+
+/**
+ *  \brief Get whether integer scales are forced for resolution-independent rendering
+ *
+ *  \param renderer The renderer from which integer scaling should be queried.
+ *
+ *  \sa SDL_RenderSetIntegerScale()
+ */
+extern DECLSPEC SDL_bool SDLCALL SDL_RenderGetIntegerScale(SDL_Renderer * renderer);
+
 /**
  *  \brief Set the drawing area for rendering on the current target.
  *
diff --git a/src/render/SDL_render.c b/src/render/SDL_render.c
index 923973ec78d85..23df884860020 100644
--- a/src/render/SDL_render.c
+++ b/src/render/SDL_render.c
@@ -1154,7 +1154,19 @@ UpdateLogicalSize(SDL_Renderer *renderer)
     /* Clear the scale because we're setting viewport in output coordinates */
     SDL_RenderSetScale(renderer, 1.0f, 1.0f);
 
-    if (SDL_fabs(want_aspect-real_aspect) < 0.0001) {
+    if (renderer->integer_scale) {
+        if (want_aspect > real_aspect) {
+            scale = w / renderer->logical_w;
+        } else {
+            scale = h / renderer->logical_h;
+        }
+        viewport.w = (int)SDL_ceil(renderer->logical_w * scale);
+        viewport.x = (w - viewport.w) / 2;
+        viewport.h = (int)SDL_ceil(renderer->logical_h * scale);
+        viewport.y = (h - viewport.h) / 2;
+
+        SDL_RenderSetViewport(renderer, &viewport);
+    } else if (SDL_fabs(want_aspect-real_aspect) < 0.0001) {
         /* The aspect ratios are the same, just scale appropriately */
         scale = (float)w / renderer->logical_w;
         SDL_RenderSetViewport(renderer, NULL);
@@ -1215,6 +1227,24 @@ SDL_RenderGetLogicalSize(SDL_Renderer * renderer, int *w, int *h)
     }
 }
 
+int
+SDL_RenderSetIntegerScale(SDL_Renderer * renderer, SDL_bool enable)
+{
+    CHECK_RENDERER_MAGIC(renderer, -1);
+
+    renderer->integer_scale = enable;
+
+    return UpdateLogicalSize(renderer);
+}
+
+SDL_bool
+SDLCALL SDL_RenderGetIntegerScale(SDL_Renderer * renderer)
+{
+    CHECK_RENDERER_MAGIC(renderer, SDL_FALSE);
+
+    return renderer->integer_scale;
+}
+
 int
 SDL_RenderSetViewport(SDL_Renderer * renderer, const SDL_Rect * rect)
 {
diff --git a/src/render/SDL_sysrender.h b/src/render/SDL_sysrender.h
index 19dfe8e6416bc..378fc4d972669 100644
--- a/src/render/SDL_sysrender.h
+++ b/src/render/SDL_sysrender.h
@@ -135,6 +135,9 @@ struct SDL_Renderer
     int logical_w_backup;
     int logical_h_backup;
 
+    /* Whether or not to force the viewport to even integer intervals */
+    SDL_bool integer_scale;
+
     /* The drawable area within the window */
     SDL_Rect viewport;
     SDL_Rect viewport_backup;