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2-Pt Persp. select: Avoid div-by-zero crash

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h/t Pere
This commit is contained in:
Bill Kendrick 2024-01-20 15:05:46 -08:00
parent 4496e007a1
commit f8c8b9b6a7
2 changed files with 27 additions and 19 deletions
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43
magic/src/n_pt_persp.c
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@ -15,8 +15,9 @@
axon. & oblique drawing modes.
by Bill Kendrick <bill@newbreedsoftware.com>
with help from Pere Pujal Carabantes
December 12, 2023 - January 16, 2024
December 12, 2023 - January 20, 2024
*/
#include <stdio.h>
@ -1527,32 +1528,38 @@ void n_pt_persp_draw_points(magic_api * api, int tool, SDL_Surface * canvas) {
x2 = 0;
}
slope = ((float) a1_pt_y - (float) y1) / ((float) a1_pt_x - (float) x1);
y2 = y1 + (x2 - x1) * slope;
if (a1_pt_x != x1) {
slope = ((float) a1_pt_y - (float) y1) / ((float) a1_pt_x - (float) x1);
y2 = y1 + (x2 - x1) * slope;
api->line((void *) api, tool, canvas, NULL,
x1, y1, x2, y2, 6,
n_pt_persp_line_xor_callback);
api->line((void *) api, tool, canvas, NULL,
x1, y1, x2, y2, 6,
n_pt_persp_line_xor_callback);
/* Some vertical lines between the diagonals */
if (l == 0) {
for (m = 0; m < 8; m++) {
int xx, yy1, yy2;
int m_scale[8] = {-8,-4,-2,-1,1,2,4,8};
/* Some vertical lines between the diagonals */
if (l == 0) {
for (m = 0; m < 8; m++) {
int xx, yy1, yy2;
int m_scale[8] = {-8,-4,-2,-1,1,2,4,8};
xx = a1_pt_x + ((float) (canvas->w / 10) * (float) m_scale[m]);
yy1 = a1_pt_y + (a1_pt_x - xx) * slope;
yy2 = a1_pt_y + (xx - a1_pt_x) * slope;
xx = a1_pt_x + ((float) (canvas->w / 10) * (float) m_scale[m]);
yy1 = a1_pt_y + (a1_pt_x - xx) * slope;
yy2 = a1_pt_y + (xx - a1_pt_x) * slope;
api->line((void *) api, tool, canvas, NULL,
xx, yy1, xx, yy2, 3,
n_pt_persp_line_xor_callback);
api->line((void *) api, tool, canvas, NULL,
xx, yy1, xx, yy2, 3,
n_pt_persp_line_xor_callback);
}
}
}
}
} else if (tool == TOOL_2PT_SELECT) {
/* 2-point perspective */
if (abs(a2_pt_x[0] - a2_pt_x[1]) < SNAP) {
a2_pt_x[1] = a2_pt_x[0] + SNAP;
}
for (i = 0; i < 2; i++) {
n_pt_persp_draw_one_point(api, canvas, a2_pt_x[i], a2_pt_y[i], i);
}
@ -1571,7 +1578,7 @@ void n_pt_persp_draw_points(magic_api * api, int tool, SDL_Surface * canvas) {
x = (a2_pt_x[0] + a2_pt_x[1]) / 2;
/* Perpendicular-to-horizon line */
if (slope == 0.0 || slope == M_PI) {
if (slope == 0.0 || slope == M_PI) { // FIXME: M_PI, really? -bjk 2024.01.20
x1 = x;
y1 = 0;
x2 = x;