Zoom effect: no ghosting at high resolutions

The scope's screen effect (a warp: copies of the screen scaled a little
from the center, blended outside the scope's mask) spreads its copies by a
radius in the Xbox's pixels. At 640x480 the few copies blended into a
radial blur; at several screen pixels to the Xbox's one they stood apart as
sharp ghosts. The native builds keep the spread and split it into that
many times the passes (halo_screen_scale), each a step of it.

(cherry picked from commit b7fa7f742a72924514eef69d50daf31ef7f7f836)
(cherry picked from commit d1b40a6fc74ab46641313a6e0095e596494a1e7b)

Without its #ifdef HALO_LINUX, which OpenCE's builds never define (it compiled to nothing), and with the copied parameters declared with the others (gnu89).

(cherry picked from commit 763567dcc7ad8e6a851fec6bb5cb9f9e10452579)

port/linux/include/halo_linux_source_fixups.h

@@ -47,6 +47,8 @@ unsigned char custom_edition_vehicle_placement_allowed(struct scenario_object_da
 /* the width of the screen the game draws, 480 lines tall: the device's or
 the display's shape, or 640 (port/linux/src/d3d8_gl.c) */
 long halo_screen_width(void);
+/* the screen's pixels to the Xbox's one (port/linux/src/d3d8_gl.c) */
+float halo_screen_scale(void);
 /* takes up a new width between frames (F11); returns the width */
 long halo_screen_commit(void);
 /* the shadow maps' pixels for each of their 128 texels each way, a power of

port/linux/src/d3d8_gl.c

@@ -242,6 +242,14 @@ float halo_screen_pixel_scale(void)
 	return screen_scale[1];
 }
 
+/* how many pixels the screen's targets draw to the Xbox's one, the larger
+of the two ways (the screen effects' convolutions: rasterizer_xbox_screen_effect.c) */
+float halo_screen_scale(void)
+{
+	halo_screen_width();
+	return screen_scale[0] > screen_scale[1] ? screen_scale[0] : screen_scale[1];
+}
+
 /* display.shadow_resolution: the size the shadow maps are drawn at.
 
 Each object's shadow is drawn from above into a 128x128 map, blurred into

source/rasterizer/xbox/rasterizer_xbox_screen_effect.c

@@ -492,6 +492,28 @@ void _rasterizer_screen_effect(
 		real_rectangle2d vertex_bounds;
 		unsigned long light_enhancement_input;
 		unsigned long desaturation_input;
+		struct rasterizer_cinematic_screen_effect_parameters scaled_parameters;
+
+		/* port: the native builds draw the screen at several pixels to the
+		Xbox's one (halo_screen_scale): a convolution's few copies of the
+		screen, apart by its radius in the Xbox's pixels, blended into a blur
+		at 640x480, and at four times the pixels they stand apart as sharp
+		ghosts (the zoom's warp). The same spread in that many times the
+		passes, each a step of it, blends them again. */
+		if (parameters->convolution_type != _rasterizer_screen_effect_convolution_type_none && !parameters->video_on)
+		{
+			long steps = (long)(halo_screen_scale() + 0.999f);
+
+			if (steps > 6)
+				steps = 6;
+			if (steps > 1)
+			{
+				scaled_parameters = *parameters;
+				scaled_parameters.convolution_radius /= (real)steps;
+				parameters = &scaled_parameters;
+				pass_count *= (short)steps;
+			}
+		}
 
 		if (parameters->video_on)
 		{