From e4ca82489c1fbbf95bb80f33066d3317682a7942 Mon Sep 17 00:00:00 2001
From: Guillaume Melquiond <guillaume.melquiond@gmail.com>
Date: Tue, 10 Aug 2010 12:08:19 +0000
Subject: [PATCH] Replaced usage of get_union_rect by intersect_rects,

...as the function was actually computing the intersection of two
rectangles. Added a proper function for computing unions.
---
 src/gui/widgets/scrollbar_container.cpp |  3 +-
 src/gui/widgets/widget.cpp              |  2 +-
 src/sdl_utils.cpp                       | 38 +++++++++++--------------
 src/sdl_utils.hpp                       | 12 +-------
 4 files changed, 19 insertions(+), 36 deletions(-)

diff --git a/src/gui/widgets/scrollbar_container.cpp b/src/gui/widgets/scrollbar_container.cpp
index e1c7701ca9e..2257c3924f1 100644
--- a/src/gui/widgets/scrollbar_container.cpp
+++ b/src/gui/widgets/scrollbar_container.cpp
@@ -390,8 +390,7 @@ void tscrollbar_container::set_visible_area(const SDL_Rect& area)
 	tcontainer_::set_visible_area(area);
 
 	// Now get the visible part of the content.
-	content_visible_area_ =
-			get_rect_union(area, content_->get_rect());
+	content_visible_area_ = intersect_rects(area, content_->get_rect());
 
 	content_grid_->set_visible_area(content_visible_area_);
 }
diff --git a/src/gui/widgets/widget.cpp b/src/gui/widgets/widget.cpp
index 1fb0efbca46..0aa3b782ec5 100644
--- a/src/gui/widgets/widget.cpp
+++ b/src/gui/widgets/widget.cpp
@@ -238,7 +238,7 @@ twidget::tdrawing_action twidget::get_drawing_action() const
 
 void twidget::set_visible_area(const SDL_Rect& area)
 {
-	clip_rect_ = get_rect_union(area, get_rect());
+	clip_rect_ = intersect_rects(area, get_rect());
 
 	if(clip_rect_ == get_rect()) {
 		drawing_action_ = DRAWN;
diff --git a/src/sdl_utils.cpp b/src/sdl_utils.cpp
index a4ff1a6dcd8..a1d6c4a2b4f 100644
--- a/src/sdl_utils.cpp
+++ b/src/sdl_utils.cpp
@@ -106,32 +106,26 @@ SDL_Rect intersect_rects(SDL_Rect const &rect1, SDL_Rect const &rect2)
 	SDL_Rect res;
 	res.x = std::max<int>(rect1.x, rect2.x);
 	res.y = std::max<int>(rect1.y, rect2.y);
-	res.w = std::max<int>(std::min<int>(rect1.x + rect1.w, rect2.x + rect2.w) - res.x, 0);
-	res.h = std::max<int>(std::min<int>(rect1.y + rect1.h, rect2.y + rect2.h) - res.y, 0);
+	int w = std::min<int>(rect1.x + rect1.w, rect2.x + rect2.w) - res.x;
+	int h = std::min<int>(rect1.y + rect1.h, rect2.y + rect2.h) - res.y;
+	if (w <= 0 || h <= 0) return empty_rect;
+	res.w = w;
+	res.h = h;
 	return res;
 }
 
-SDL_Rect get_rect_union(SDL_Rect const &rect1, SDL_Rect const& rect2) {
-	const int left_side = std::max(rect1.x, rect2.x);
-	const int right_side = std::min(rect1.x + rect1.w, rect2.x + rect2.w);
-	if(left_side > right_side) {
-		return empty_rect;
-	}
-
-	const int top_side = std::max(rect1.y, rect2.y);
-	const int bottom_side = std::min(rect1.y + rect1.h, rect2.y + rect2.h);
-	if(top_side > bottom_side) {
-		return empty_rect;
-	}
-
-	SDL_Rect result = create_rect(
-			left_side,
-			top_side,
-			right_side - left_side,
-			bottom_side - top_side);
-
-	return result;
+SDL_Rect union_rects(SDL_Rect const &rect1, SDL_Rect const &rect2)
+{
+	if (rect1.w == 0 || rect1.h == 0) return rect2;
+	if (rect2.w == 0 || rect2.h == 0) return rect1;
+	SDL_Rect res;
+	res.x = std::min<int>(rect1.x, rect2.x);
+	res.y = std::min<int>(rect1.y, rect2.y);
+	res.w = std::max<int>(rect1.x + rect1.w, rect2.x + rect2.w) - res.x;
+	res.h = std::max<int>(rect1.y + rect1.h, rect2.y + rect2.h) - res.y;
+	return res;
 }
+
 SDL_Rect create_rect(const int x, const int y, const int w, const int h)
 {
 	SDL_Rect rect;
diff --git a/src/sdl_utils.hpp b/src/sdl_utils.hpp
index 86ca3c4e3ca..f61482633a8 100644
--- a/src/sdl_utils.hpp
+++ b/src/sdl_utils.hpp
@@ -56,18 +56,8 @@ SDLKey sdl_keysym_from_name(std::string const &keyname);
 bool point_in_rect(int x, int y, const SDL_Rect& rect);
 bool rects_overlap(const SDL_Rect& rect1, const SDL_Rect& rect2);
 SDL_Rect intersect_rects(SDL_Rect const &rect1, SDL_Rect const &rect2);
+SDL_Rect union_rects(const SDL_Rect &rect1, const SDL_Rect &rect2);
 
-/**
- * Returns the union of two rectangles.
- *
- * @param rect1                   The first rectangle.
- * @param rect2                   The second rectangle.
- *
- * @returns                       The union of the two rectangles. If the
- *                                rectangles don't intersect and empty
- *                                rectangle is returned.
- */
-SDL_Rect get_rect_union(const SDL_Rect& rect1, const SDL_Rect& rect2);
 /**
  *  Creates an empty SDL_Rect.
  *