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kmatch98kmatch98
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Fix off-by-one error, simplify the logic, add comments
1 parent d600759 commit 37e85ae

1 file changed

Lines changed: 31 additions & 37 deletions

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‎shared-module/displayio/Shape.c‎

Lines changed: 31 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -38,20 +38,20 @@ void common_hal_displayio_shape_construct(displayio_shape_t *self, uint32_t widt
3838
self->width = width;
3939
if (self->mirror_x) {
4040
width /= 2;
41-
width += self->width % 2 - 1;
41+
width += self->width % 2;
4242
}
4343
self->half_width = width;
4444

4545
self->height = height;
4646
if (self->mirror_y) {
4747
height /= 2;
48-
height += self->height % 2 - 1;
48+
height += self->height % 2;
4949
}
5050
self->half_height = height;
5151

5252
self->data = m_malloc(height * sizeof(uint32_t), false);
5353

54-
for (uint16_t i = 0; i <= height; i++) {
54+
for (uint16_t i = 0; i < height; i++) {
5555
self->data[2 * i] = 0;
5656
self->data[2 * i + 1] = width;
5757
}
@@ -63,69 +63,63 @@ void common_hal_displayio_shape_construct(displayio_shape_t *self, uint32_t widt
6363
}
6464

6565
void common_hal_displayio_shape_set_boundary(displayio_shape_t *self, uint16_t y, uint16_t start_x, uint16_t end_x) {
66-
if (y < 0 || y >= self->height || (self->mirror_y && y > self->half_height)) {
66+
if (y < 0 || y >= self->height || (self->mirror_y && y >= self->half_height)) {
6767
mp_raise_ValueError(translate("y value out of bounds"));
6868
}
69-
if (start_x < 0 || start_x > self->width || end_x < 0 || end_x > self->width) {
69+
if (start_x < 0 || start_x >= self->width || end_x < 0 || end_x >= self->width) {
7070
mp_raise_ValueError(translate("x value out of bounds"));
7171
}
72-
uint16_t half_width = self->width / 2 - 1 + self->width % 2;
73-
if (self->mirror_x && (start_x > half_width || end_x > half_width)) {
74-
mp_raise_ValueError_varg(translate("Maximum x value when mirrored is %d"), half_width);
72+
if (self->mirror_x && (start_x >= self->half_width || end_x >= self->half_width)) {
73+
mp_raise_ValueError_varg(translate("Maximum x value when mirrored is %d"), self->half_width);
7574
}
7675

77-
uint16_t lower_x, upper_x;
76+
uint16_t lower_x, upper_x, lower_y, upper_y;
7877

79-
// find x-boundaries for updating based on current data and start_x, end_x
78+
// find x-boundaries for updating based on current data and start_x, end_x, and mirror_x
8079
lower_x = MIN(start_x, self->data[2 * y]);
8180

8281
if (self->mirror_x) {
83-
upper_x = self->width-lower_x;
82+
upper_x = self->width - lower_x + 1; // dirty rectangles are treated with max value exclusive
8483
} else {
85-
upper_x = 1 + MAX(end_x, self->data[2 * y + 1]);
84+
upper_x = MAX(end_x, self->data[2 * y + 1]) + 1; // dirty rectangles are treated with max value exclusive
8685
}
8786

88-
self->data[2 * y] = start_x;
87+
// find y-boundaries based on y and mirror_y
88+
lower_y = y;
89+
90+
if (self->mirror_y) {
91+
upper_y = self->height - lower_y + 1; // dirty rectangles are treated with max value exclusive
92+
} else {
93+
upper_y = y + 1; // dirty rectangles are treated with max value exclusive
94+
}
95+
96+
self->data[2 * y] = start_x; // update the data array with the new boundaries
8997
self->data[2 * y + 1] = end_x;
9098

9199
if (self->dirty_area.x1 == self->dirty_area.x2) { // Dirty region is empty
92-
self->dirty_area.x1=lower_x;
93-
self->dirty_area.x2=upper_x;
94-
self->dirty_area.y1 = y;
95-
if (self->mirror_y) {
96-
self->dirty_area.y2 = self->height-y;
97-
} else {
98-
self->dirty_area.y2 = y+1;
99-
}
100-
} else { // Dirty region is not empty
100+
self->dirty_area.x1 = lower_x;
101+
self->dirty_area.x2 = upper_x;
102+
self->dirty_area.y1 = lower_y;
103+
self->dirty_area.y2 = upper_y;
101104

105+
} else { // Dirty region is not empty
102106
self->dirty_area.x1 = MIN(lower_x, self->dirty_area.x1);
103107
self->dirty_area.x2 = MAX(upper_x, self->dirty_area.x2);
104108

105-
if (y < self->dirty_area.y1) {
106-
self->dirty_area.y1=y;
107-
if (self->mirror_y) { // if y is mirrored and the lower y was updated, the upper y must be updated too
108-
self->dirty_area.y2=self->height-y;
109-
}
110-
}
111-
else {
112-
if ( !self->mirror_y && (y >= self->dirty_area.y2) ) { // y is not mirrored
113-
self->dirty_area.y2=y+1;
114-
}
115-
}
109+
self->dirty_area.y1 = MIN(lower_y, self->dirty_area.y1);
110+
self->dirty_area.y2 = MAX(upper_y, self->dirty_area.y2);
116111
}
117-
118112
}
119113

120114
uint32_t common_hal_displayio_shape_get_pixel(void *obj, int16_t x, int16_t y) {
121115
displayio_shape_t *self = obj;
122116
if (x >= self->width || x < 0 || y >= self->height || y < 0) {
123117
return 0;
124118
}
125-
if (self->mirror_x && x > self->half_width) {
126-
x = self->width - 1 - x;
119+
if (self->mirror_x && x >= self->half_width) {
120+
x = self->width - x - 1;
127121
}
128-
if (self->mirror_y && y > self->half_height) {
122+
if (self->mirror_y && y >= self->half_height) {
129123
y = self->height - y - 1;
130124
}
131125
uint16_t start_x = self->data[2 * y];

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