line-endpoints.c

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/*
 
MIT License
 
Copyright (c) 2026 PCSX-Redux authors
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
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The above copyright notice and this permission notice shall be included in all
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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SOFTWARE.
 
*/
 
// Line endpoints suite. GP0(0x40) flat untextured line - two vertex
// words after the command. Documents:
//   - Whether start AND end pixels are both drawn (inclusive on both ends).
//   - Bresenham octant symmetry: same shape across +X+Y, -X+Y, etc.
//   - Zero-length lines (start == end): does anything draw?
//   - Shallow vs steep lines (major axis selection).
//   - Diagonal at exactly 45 deg vs slope-0 / slope-infinity edge cases.
 
CESTER_BODY(
 
// Horizontal 1px line at y=10 from x=5 to x=10.
static void rasterDrawLineH(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 16);
    rasterFlatLine(RASTER_CMD_GREEN, 5, 10, 10, 10);
    rasterFlushPrimitive();
}
 
// Vertical 1px line at x=10 from y=5 to y=10.
static void rasterDrawLineV(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 16);
    rasterFlatLine(RASTER_CMD_RED, 10, 5, 10, 10);
    rasterFlushPrimitive();
}
 
// Diagonal +45 deg from (5,5) to (10,10).
static void rasterDrawLineD45(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 16);
    rasterFlatLine(RASTER_CMD_BLUE, 5, 5, 10, 10);
    rasterFlushPrimitive();
}
 
// Diagonal -45 deg from (5,10) to (10,5).
static void rasterDrawLineDN45(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 16);
    rasterFlatLine(RASTER_CMD_WHITE, 5, 10, 10, 5);
    rasterFlushPrimitive();
}
 
// Zero-length line: same start and end point.
static void rasterDrawLineZero(void) {
    rasterReset();
    rasterClearTestRegion(16, 16, 16, 8);
    rasterFlatLine(RASTER_CMD_RED, 20, 20, 20, 20);
    rasterFlushPrimitive();
}
 
// Shallow slope line (more horizontal than vertical): (0,0) to (10,3).
// Major axis is X. Tests Bresenham major-axis selection.
static void rasterDrawLineShallow(void) {
    rasterReset();
    rasterClearTestRegion(0, 0, 16, 8);
    rasterFlatLine(RASTER_CMD_GREEN, 0, 0, 10, 3);
    rasterFlushPrimitive();
}
 
)  // CESTER_BODY
 
// --------------------------------------------------------------------------
// Horizontal line (5,10) - (10,10)
// --------------------------------------------------------------------------
 
CESTER_TEST(lineH_before_start_pixel_4_10, gpu_raster_phase2,
    rasterDrawLineH();
    ASSERT_PIXEL_EQ(EXPECT_LINE_H_PIXEL_4_10, 4, 10);
)
 
CESTER_TEST(lineH_start_pixel_5_10, gpu_raster_phase2,
    rasterDrawLineH();
    ASSERT_PIXEL_EQ(EXPECT_LINE_H_PIXEL_5_10, 5, 10);
)
 
CESTER_TEST(lineH_interior_pixel_7_10, gpu_raster_phase2,
    rasterDrawLineH();
    ASSERT_PIXEL_EQ(EXPECT_LINE_H_PIXEL_7_10, 7, 10);
)
 
CESTER_TEST(lineH_end_pixel_10_10_inclusive, gpu_raster_phase2,
    rasterDrawLineH();
    ASSERT_PIXEL_EQ(EXPECT_LINE_H_PIXEL_10_10, 10, 10);
)
 
CESTER_TEST(lineH_past_end_pixel_11_10, gpu_raster_phase2,
    rasterDrawLineH();
    ASSERT_PIXEL_EQ(EXPECT_LINE_H_PIXEL_11_10, 11, 10);
)
 
CESTER_TEST(lineH_below_line_pixel_5_11, gpu_raster_phase2,
    rasterDrawLineH();
    ASSERT_PIXEL_EQ(EXPECT_LINE_H_PIXEL_5_11, 5, 11);
)
 
// --------------------------------------------------------------------------
// Vertical line (10,5) - (10,10)
// --------------------------------------------------------------------------
 
CESTER_TEST(lineV_before_start_pixel_10_4, gpu_raster_phase2,
    rasterDrawLineV();
    ASSERT_PIXEL_EQ(EXPECT_LINE_V_PIXEL_10_4, 10, 4);
)
 
CESTER_TEST(lineV_start_pixel_10_5, gpu_raster_phase2,
    rasterDrawLineV();
    ASSERT_PIXEL_EQ(EXPECT_LINE_V_PIXEL_10_5, 10, 5);
)
 
CESTER_TEST(lineV_interior_pixel_10_7, gpu_raster_phase2,
    rasterDrawLineV();
    ASSERT_PIXEL_EQ(EXPECT_LINE_V_PIXEL_10_7, 10, 7);
)
 
CESTER_TEST(lineV_end_pixel_10_10_inclusive, gpu_raster_phase2,
    rasterDrawLineV();
    ASSERT_PIXEL_EQ(EXPECT_LINE_V_PIXEL_10_10, 10, 10);
)
 
CESTER_TEST(lineV_past_end_pixel_10_11, gpu_raster_phase2,
    rasterDrawLineV();
    ASSERT_PIXEL_EQ(EXPECT_LINE_V_PIXEL_10_11, 10, 11);
)
 
// --------------------------------------------------------------------------
// Diagonal +45 deg (5,5) - (10,10)
// --------------------------------------------------------------------------
 
CESTER_TEST(lineD45_start_pixel_5_5, gpu_raster_phase2,
    rasterDrawLineD45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_D45_PIXEL_5_5, 5, 5);
)
 
CESTER_TEST(lineD45_interior_pixel_7_7, gpu_raster_phase2,
    rasterDrawLineD45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_D45_PIXEL_7_7, 7, 7);
)
 
CESTER_TEST(lineD45_end_pixel_10_10, gpu_raster_phase2,
    rasterDrawLineD45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_D45_PIXEL_10_10, 10, 10);
)
 
CESTER_TEST(lineD45_off_diag_pixel_5_6, gpu_raster_phase2,
    rasterDrawLineD45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_D45_PIXEL_5_6, 5, 6);
)
 
CESTER_TEST(lineD45_off_diag_pixel_6_5, gpu_raster_phase2,
    rasterDrawLineD45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_D45_PIXEL_6_5, 6, 5);
)
 
// --------------------------------------------------------------------------
// Diagonal -45 deg (5,10) - (10,5)
// --------------------------------------------------------------------------
 
CESTER_TEST(lineDN45_start_pixel_5_10, gpu_raster_phase2,
    rasterDrawLineDN45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_DN45_PIXEL_5_10, 5, 10);
)
 
CESTER_TEST(lineDN45_interior_pixel_7_8, gpu_raster_phase2,
    rasterDrawLineDN45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_DN45_PIXEL_7_8, 7, 8);
)
 
CESTER_TEST(lineDN45_end_pixel_10_5, gpu_raster_phase2,
    rasterDrawLineDN45();
    ASSERT_PIXEL_EQ(EXPECT_LINE_DN45_PIXEL_10_5, 10, 5);
)
 
// --------------------------------------------------------------------------
// Zero-length line (20,20) - (20,20)
// --------------------------------------------------------------------------
 
CESTER_TEST(lineZero_start_pixel_20_20, gpu_raster_phase2,
    rasterDrawLineZero();
    ASSERT_PIXEL_EQ(EXPECT_LINE_ZERO_PIXEL_20_20, 20, 20);
)
 
CESTER_TEST(lineZero_neighbor_pixel_21_20, gpu_raster_phase2,
    rasterDrawLineZero();
    ASSERT_PIXEL_EQ(EXPECT_LINE_ZERO_PIXEL_21_20, 21, 20);
)
 
// --------------------------------------------------------------------------
// Shallow line (0,0) - (10,3): major axis is X
// --------------------------------------------------------------------------
 
CESTER_TEST(lineShallow_start_pixel_0_0, gpu_raster_phase2,
    rasterDrawLineShallow();
    ASSERT_PIXEL_EQ(EXPECT_LINE_SHALLOW_PIXEL_0_0, 0, 0);
)
 
CESTER_TEST(lineShallow_midpoint_pixel_5_2, gpu_raster_phase2,
    rasterDrawLineShallow();
    ASSERT_PIXEL_EQ(EXPECT_LINE_SHALLOW_PIXEL_5_2, 5, 2);
)
 
CESTER_TEST(lineShallow_end_pixel_10_3, gpu_raster_phase2,
    rasterDrawLineShallow();
    ASSERT_PIXEL_EQ(EXPECT_LINE_SHALLOW_PIXEL_10_3, 10, 3);
)
 
CESTER_TEST(lineShallow_x_2_y_0_bresenham_choice, gpu_raster_phase2,
    rasterDrawLineShallow();
    // At x=2, the Bresenham accumulator should have stepped y to 1.
    // Pixel (2, 0) on the original major-axis row should be empty if
    // the line steps y up before x=2. Verifies major-axis stepping.
    ASSERT_PIXEL_EQ(EXPECT_LINE_SHALLOW_PIXEL_2_0, 2, 0);
)