Add a new image tiling mode: "tile_highres" for high-DPI tiled images.

The other options "tile" and "tile_center" work in draw space,
which is consistent with past behaviour, but doesn't look as nice.

data/gui/widget/window_borderless.cfg

@@ -23,7 +23,7 @@
 					w = "(width)"
 					h = "(height)"
 					name = "dialogs/opaque-background.png"
-					resize_mode = "tile"
+					resize_mode = "tile_highres"
 				[/image]
 
 				{_BACKGROUND_DRAW}

data/gui/widget/window_default.cfg

@@ -48,7 +48,7 @@
 					w = "(width - 4)"
 					h = "(height - 4)"
 					name = "dialogs/{BASE_NAME}-background.png"
-					resize_mode = "tile"
+					resize_mode = "tile_highres"
 				[/image]
 
 			[/draw]
@@ -152,7 +152,7 @@
 					w = "(width)"
 					h = "(height)"
 					name = "dialogs/menu-background.png"
-					resize_mode = "tile"
+					resize_mode = "tile_highres"
 				[/image]
 
 				[rectangle]

data/schema/gui.cfg

@@ -31,7 +31,7 @@
     [/type]
     [type]
         name=resize_mode
-        value="scale|scale_sharp|stretch|tile|tile_center"
+        value="scale|scale_sharp|stretch|tile|tile_center|tile_highres"
     [/type]
     [type]
         name=scrollbar_mode

src/draw.cpp

@@ -270,11 +270,11 @@ void draw::flipped(const texture& tex, bool flip_h, bool flip_v)
 }
 
 
+// TODO: highdpi - maybe expose this mirrored mode to WML somehow
 void draw::tiled(const texture& tex, const SDL_Rect& dst, bool centered,
 	bool mirrored)
 {
 	if (!tex) { return; }
-	// TODO: highdpi - should this draw at full res? Or game res? For now it's using game res. To draw in higher res, width and height would have to be specified.
 
 	// Reduce clip to dst.
 	auto clipper = draw::reduce_clip(dst);
@@ -297,6 +297,38 @@ void draw::tiled(const texture& tex, const SDL_Rect& dst, bool centered,
 	}
 }
 
+void draw::tiled_highres(const texture& tex, const SDL_Rect& dst,
+	bool centered, bool mirrored)
+{
+	if (!tex) { return; }
+
+	const int pixel_scale = CVideo::get_singleton().get_pixel_scale();
+
+	// Reduce clip to dst.
+	auto clipper = draw::reduce_clip(dst);
+
+	const auto info = tex.get_info();
+	const float w = float(info.w) / float(pixel_scale);
+	const float h = float(info.h) / float(pixel_scale);
+	const float xoff = centered ? (dst.w - w) / 2 : 0.0f;
+	const float yoff = centered ? (dst.h - h) / 2 : 0.0f;
+
+	// Just blit the image however many times is necessary.
+	bool vf = false;
+	SDL_FRect t{dst.x - xoff, dst.y - yoff, w, h};
+	for (; t.y < dst.y + dst.h; t.y += t.h, vf = !vf) {
+		bool hf = false;
+		for (t.x = dst.x - xoff; t.x < dst.x + dst.w; t.x += t.w, hf = !hf) {
+			if (mirrored) {
+				SDL_RendererFlip flip = get_flip(hf, vf);
+				SDL_RenderCopyExF(renderer(), tex, nullptr, &t, 0.0, nullptr, flip);
+			} else {
+				SDL_RenderCopyF(renderer(), tex, nullptr, &t);
+			}
+		}
+	}
+}
+
 
 /***************************/
 /* RAII state manipulation */

src/draw.hpp

@@ -238,6 +238,8 @@ void flipped(const texture& tex, bool flip_h = true, bool flip_v = false);
 /**
  * Tile a texture to fill a region.
  *
+ * This function tiles the texture in draw-space.
+ *
  * The texture may be aligned either with its center at the center
  * of the region, or with its top-left corner at the top-left corner
  * of the region.
@@ -256,6 +258,17 @@ void tiled(const texture& tex,
 	bool mirrored = false
 );
 
+/** Tile a texture to fill a region.
+ *
+ * This function tiles the texture in output space. It is otherwise
+ * identical to draw::tiled().
+ */
+void tiled_highres(const texture& tex,
+	const SDL_Rect& dst,
+	bool centered = false,
+	bool mirrored = false
+);
+
 
 /***************************/
 /* RAII state manipulation */

src/gui/core/canvas.cpp

@@ -431,6 +431,9 @@ void image_shape::draw(
 	case (resize_mode::tile_center):
 		draw::tiled(tex, adjusted_draw_loc, true, mirror_(variables));
 		break;
+	case resize_mode::tile_highres:
+		draw::tiled_highres(tex, adjusted_draw_loc, false, mirror_(variables));
+		break;
 	case resize_mode::stretch:
 		// Stretching is identical to scaling in terms of handling.
 		// Is this intended? That's what previous code was doing.
@@ -456,6 +459,8 @@ image_shape::resize_mode image_shape::get_resize_mode(const std::string& resize_
 		return resize_mode::tile;
 	} else if(resize_mode == "tile_center") {
 		return resize_mode::tile_center;
+	} else if(resize_mode == "tile_highres") {
+		return resize_mode::tile_highres;
 	} else if(resize_mode == "stretch") {
 		return resize_mode::stretch;
 	} else if(resize_mode == "scale_sharp") {

src/gui/core/canvas_private.hpp

@@ -386,6 +386,7 @@ private:
 		stretch,
 		tile,
 		tile_center,
+		tile_highres,
 	};
 
 	/** Converts a string to a resize mode. */