rectangle-clipping.c

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// Rectangle clipping suite. GP0(0x60) flat variable-size rectangle.
// Drawing area = (0,0) .. (1024, 512) by default. Tests:
//   - Rect entirely inside the draw area (R1).
//   - Rect with top-left outside the draw area (R2). Top-left clipping.
//   - Rect that exactly equals the draw area edge.
//   - Rect with negative coordinates after drawing offset.
 
CESTER_BODY(
 
// R1: 4x4 rectangle at (10, 10), GREEN. Fully inside draw area.
static void rasterDrawRectR1(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 32, 32);
    rasterFlatRect(RASTER_CMD_GREEN, 10, 10, 4, 4);
    rasterFlushPrimitive();
}
 
// R2: 8x8 rectangle starting at (-2, -2), GREEN. Top-left 4x4 quadrant
// of the rect is outside the draw area; only the bottom-right 6x6 region
// remains and should fill VRAM (0,0)..(5,5).
//
// Note: GP0(0x60) takes UNSIGNED 16-bit coordinates in the second word
// (x | y<<16). Negative -2 sign-extends to 0xfffe which would naturally
// be a huge X. But the drawing-area clipping should clamp this. The
// observation IS the test - if the GPU treats -2 as 0xfffe and clips
// everything (no draw), we want to see that in the OBS log.
//
// To get a meaningful test of "negative top-left clipping" we instead
// shift the drawing area so the test rect crosses its top-left edge
// with VALID 11-bit coordinates. Set draw area to (4, 4)..(end), draw
// rect at (2, 2) size 6x6. Then VRAM (4,4)..(7,7) should fill and
// VRAM (2,2)..(3,3) should stay sentinel.
static void rasterDrawRectR2(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 16);
    // Shrink draw area to (4, 4)..(16, 16).
    setDrawingArea(4, 4, 16, 16);
    rasterFlatRect(RASTER_CMD_GREEN, 2, 2, 6, 6);
    rasterFlushPrimitive();
}
 
)  // CESTER_BODY
 
// --------------------------------------------------------------------------
// Rect R1: fully inside draw area
// --------------------------------------------------------------------------
 
CESTER_TEST(rectR1_top_left, gpu_raster_phase1,
    rasterDrawRectR1();
    ASSERT_PIXEL_EQ(EXPECT_RECT_R1_PIXEL_10_10, 10, 10);
)
 
CESTER_TEST(rectR1_bottom_right_interior, gpu_raster_phase1,
    rasterDrawRectR1();
    ASSERT_PIXEL_EQ(EXPECT_RECT_R1_PIXEL_13_13, 13, 13);
)
 
CESTER_TEST(rectR1_right_edge_excluded, gpu_raster_phase1,
    rasterDrawRectR1();
    ASSERT_PIXEL_EQ(EXPECT_RECT_R1_PIXEL_14_10, 14, 10);
)
 
CESTER_TEST(rectR1_bottom_edge_excluded, gpu_raster_phase1,
    rasterDrawRectR1();
    ASSERT_PIXEL_EQ(EXPECT_RECT_R1_PIXEL_10_14, 10, 14);
)
 
CESTER_TEST(rectR1_before_left_edge, gpu_raster_phase1,
    rasterDrawRectR1();
    ASSERT_PIXEL_EQ(EXPECT_RECT_R1_PIXEL_9_10, 9, 10);
)
 
// --------------------------------------------------------------------------
// Rect R2: top-left clipped by drawing area (4,4)
// --------------------------------------------------------------------------
//
// EXPECT_RECT_R2_PIXEL_0_0 in raster-expected.h was written assuming the
// default draw area (0,0). Here we use a shifted draw area (4,4) and
// expect the rect at (2,2) size 6x6 to fill VRAM (4,4)..(7,7) only.
// The pixels we assert against differ from the placeholders; redirect
// to the actual coordinates this test exercises.
 
CESTER_TEST(rectR2_clipped_pixel_4_4_corner, gpu_raster_phase1,
    rasterDrawRectR2();
    // (4,4) is inside both the rect and the shrunk draw area: should fill.
    ASSERT_PIXEL_EQ(RASTER_VRAM_GREEN, 4, 4);
)
 
CESTER_TEST(rectR2_clipped_pixel_7_7_bottom_right, gpu_raster_phase1,
    rasterDrawRectR2();
    // (7,7) is the last interior pixel given the rect (2,2)..(8,8)
    // exclusive right/bottom under top-left rule.
    ASSERT_PIXEL_EQ(RASTER_VRAM_GREEN, 7, 7);
)
 
CESTER_TEST(rectR2_clipped_pixel_2_2_top_left_outside_draw_area,
            gpu_raster_phase1,
    rasterDrawRectR2();
    // (2,2) is inside the rect but OUTSIDE the draw area (which starts
    // at 4). Should be clipped -> sentinel.
    ASSERT_PIXEL_UNTOUCHED(2, 2);
)
 
CESTER_TEST(rectR2_clipped_pixel_3_3_just_inside_rect_outside_draw,
            gpu_raster_phase1,
    rasterDrawRectR2();
    // (3,3) is inside the rect but just outside the shifted draw area.
    // Should be sentinel.
    ASSERT_PIXEL_UNTOUCHED(3, 3);
)
 
CESTER_TEST(rectR2_clipped_pixel_8_8_outside_rect, gpu_raster_phase1,
    rasterDrawRectR2();
    // (8,8) is past the rect's exclusive right/bottom edge.
    ASSERT_PIXEL_UNTOUCHED(8, 8);
)