draw-area.c

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/*
 
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Copyright (c) 2026 PCSX-Redux authors
 
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*/
 
// Drawing-area + drawing-offset interactions. GP0(E3) sets the area
// upper-left, GP0(E4) the area lower-right (inclusive). GP0(E5) sets
// the offset added to every primitive vertex.
//
// Documents:
//   - Offset (50, 50): primitive at logical (0,0) draws at VRAM (50,50).
//   - Offset combined with draw-area clip.
//   - Primitive at negative logical coords after offset.
 
// clang-format off
 
CESTER_BODY(
 
// Offset-A: Triangle A geometry (0,0),(4,0),(0,4) with drawing offset
// (50, 50). Expected to fill exactly the same pixel set as Triangle A
// from triangle-edges.c, shifted by (50, 50).
static void rasterDrawOffsetA(void) {
    rasterReset();
    rasterClearTestRegion(48, 48, 16, 16);
    // Also clear the original origin so we can assert it stays sentinel.
    rasterClearTestRegion(0, 0, 8, 8);
    setDrawingOffset(50, 50);
    rasterFlatTri(RASTER_CMD_RED, 0, 0, 4, 0, 0, 4);
    rasterFlushPrimitive();
}
 
// Offset-B: Drawing offset that pushes geometry partially OFF the draw
// area. Logical (-3, -3), (5, -3), (-3, 5) with offset (3, 3) gives
// destination triangle (0,0), (8,0), (0,8). The drawing-area clip is
// (0, 0)..(1024, 512) so nothing should be cut. This documents that
// offset itself does not introduce clipping when destinations are
// non-negative.
static void rasterDrawOffsetB(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 16);
    setDrawingOffset(3, 3);
    rasterFlatTri(RASTER_CMD_GREEN, -3, -3, 5, -3, -3, 5);
    rasterFlushPrimitive();
}
 
// Offset-C: Drawing offset PLUS shrunk draw area. The primitive lands
// inside VRAM but partially outside the active draw area. Should clip
// to the area, not silently extend past it.
//   Draw area: (10, 10)..(20, 20)
//   Offset: (10, 10)
//   Primitive: triangle (0,0),(8,0),(0,8) -> VRAM (10,10),(18,10),(10,18)
// All of the destination is inside the draw area, so the triangle
// should render fully. This is a sanity check that offset + draw area
// compose additively.
static void rasterDrawOffsetC(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 32, 32);
    setDrawingArea(10, 10, 20, 20);
    setDrawingOffset(10, 10);
    rasterFlatTri(RASTER_CMD_BLUE, 0, 0, 8, 0, 0, 8);
    rasterFlushPrimitive();
}
 
)  // CESTER_BODY
 
// --------------------------------------------------------------------------
// Offset A: triangle shifted by (50, 50)
// --------------------------------------------------------------------------
 
CESTER_TEST(offsetA_origin_top_left_at_50_50, gpu_raster_phase1,
    rasterDrawOffsetA();
    ASSERT_PIXEL_EQ(EXPECT_OFFSET_PIXEL_50_50, 50, 50);
)
 
CESTER_TEST(offsetA_origin_top_inner_53_50, gpu_raster_phase1,
    rasterDrawOffsetA();
    ASSERT_PIXEL_EQ(EXPECT_OFFSET_PIXEL_53_50, 53, 50);
)
 
CESTER_TEST(offsetA_right_edge_54_50_excluded, gpu_raster_phase1,
    rasterDrawOffsetA();
    ASSERT_PIXEL_EQ(EXPECT_OFFSET_PIXEL_54_50, 54, 50);
)
 
CESTER_TEST(offsetA_bottom_edge_50_54_excluded, gpu_raster_phase1,
    rasterDrawOffsetA();
    ASSERT_PIXEL_EQ(EXPECT_OFFSET_PIXEL_50_54, 50, 54);
)
 
CESTER_TEST(offsetA_origin_0_0_untouched, gpu_raster_phase1,
    rasterDrawOffsetA();
    // With offset 50,50, the logical (0,0) corner of the triangle should
    // NOT write VRAM (0,0). Sentinel confirms the offset took effect.
    ASSERT_PIXEL_EQ(EXPECT_OFFSET_PIXEL_0_0, 0, 0);
)
 
// --------------------------------------------------------------------------
// Offset B: negative logical coordinates compensated by positive offset
// --------------------------------------------------------------------------
 
CESTER_TEST(offsetB_negative_compensated_pixel_0_0, gpu_raster_phase1,
    rasterDrawOffsetB();
    // Logical (-3, -3) + offset (3, 3) = VRAM (0, 0). The triangle
    // (-3,-3)(5,-3)(-3,5) -> (0,0)(8,0)(0,8). Top-left rule says (0,0)
    // is drawn (inclusive corner).
    ASSERT_PIXEL_EQ(RASTER_VRAM_GREEN, 0, 0);
)
 
CESTER_TEST(offsetB_negative_compensated_pixel_7_0, gpu_raster_phase1,
    rasterDrawOffsetB();
    // Last drawn pixel of the top edge under top-left rule.
    ASSERT_PIXEL_EQ(RASTER_VRAM_GREEN, 7, 0);
)
 
CESTER_TEST(offsetB_negative_compensated_pixel_8_0, gpu_raster_phase1,
    rasterDrawOffsetB();
    // Right-vertex corner; top-left rule excludes.
    ASSERT_PIXEL_UNTOUCHED(8, 0);
)
 
CESTER_TEST(offsetB_negative_compensated_pixel_0_8, gpu_raster_phase1,
    rasterDrawOffsetB();
    // Bottom-vertex; bottom edge excluded.
    ASSERT_PIXEL_UNTOUCHED(0, 8);
)
 
// --------------------------------------------------------------------------
// Offset C: offset + shifted draw area compose additively
// --------------------------------------------------------------------------
 
CESTER_TEST(offsetC_compose_pixel_10_10_inside_area, gpu_raster_phase1,
    rasterDrawOffsetC();
    ASSERT_PIXEL_EQ(RASTER_VRAM_BLUE, 10, 10);
)
 
CESTER_TEST(offsetC_compose_pixel_17_10_top_inner, gpu_raster_phase1,
    rasterDrawOffsetC();
    // Logical (7,0) + offset 10 = VRAM (17,10). Inside draw area (ends
    // at 20). Under top-left rule for triangle (0,0)(8,0)(0,8), pixel
    // x=7 y=0 is the last included on the top edge.
    ASSERT_PIXEL_EQ(RASTER_VRAM_BLUE, 17, 10);
)
 
CESTER_TEST(offsetC_compose_pixel_18_10_right_vertex, gpu_raster_phase1,
    rasterDrawOffsetC();
    // Right-vertex corner excluded under top-left rule.
    ASSERT_PIXEL_UNTOUCHED(18, 10);
)
 
CESTER_TEST(offsetC_compose_pixel_9_9_before_draw_area, gpu_raster_phase1,
    rasterDrawOffsetC();
    // Just outside the shifted draw area (which starts at 10).
    ASSERT_PIXEL_UNTOUCHED(9, 9);
)