1 files changed, 85 insertions, 0 deletions
diff --git a/hitomezashi.c b/hitomezashi.c
new file mode 100644
index 0000000..c1c581e
--- /dev/null
+++ b/hitomezashi.c
@@ -0,0 +1,85 @@
+#include "hitomezashi.h"
+#include "SDL.h"
+#include <assert.h>
+
+SDL_Color HITOMEZASHI_FG_COLOUR = { .r = 0,	.g = 0,		.b = 0		};
+SDL_Color HITOMEZASHI_BG_COLOUR = { .r = 255,	.g = 255,	.b = 255	};
+
+enum Hitomezashi_State_Init_Result
+hitomezashi_state_init(
+			struct Hitomezashi_State *state,
+			int x_pattern_len, int y_pattern_len,
+			char *x_pattern, char *y_pattern,
+			int gap, int line_thickness) {
+	assert(x_pattern_len >= 0);
+	assert(y_pattern_len >= 0);
+	assert(gap >= 0);
+	assert(line_thickness > 0);
+
+	state->y_pattern_len = y_pattern_len;
+	state->x_pattern_len = x_pattern_len;
+	state->x_pattern = x_pattern;
+	state->y_pattern = y_pattern;
+	state->gap = gap;
+	state->line_thickness = line_thickness;
+	state->output_width = x_pattern_len * gap;
+	state->output_height = y_pattern_len * gap;
+
+	state->surface = SDL_CreateRGBSurface(0, state->output_width, state->output_height, 32, 0, 0, 0, 0);
+	if (!state->surface) {
+		return Hitomezashi_State_Init_Result_Err_Create_Surface;
+	}
+	return Hitomezashi_State_Init_Result_Success;
+}
+
+enum Hitomezashi_Draw_Result
+hitomezashi_draw(struct Hitomezashi_State *state) {
+	if (SDL_LockSurface(state->surface) != 0) {
+		return Hitomezashi_Draw_Result_Err_Lock_Surface;
+	}
+
+	Uint32 bg_colour = SDL_MapRGB(state->surface->format, HITOMEZASHI_BG_COLOUR.r, HITOMEZASHI_BG_COLOUR.g, HITOMEZASHI_BG_COLOUR.b);
+	Uint32 fg_colour = SDL_MapRGB(state->surface->format, HITOMEZASHI_FG_COLOUR.r, HITOMEZASHI_FG_COLOUR.g, HITOMEZASHI_FG_COLOUR.b);
+
+	SDL_FillRect(state->surface, NULL, bg_colour);
+
+	SDL_Rect rect;
+	// Draw y pattern (horizontal) lines
+	for (int i = 0; i < state->y_pattern_len; ++i) {
+		for (int j = 0; j < state->x_pattern_len; ++j) {
+			if (j % 2 == state->y_pattern[i]) {
+				rect.x = j * state->gap;
+				rect.y = i * state->gap;
+				rect.w = state->gap;
+				rect.h = state->line_thickness;
+				SDL_FillRect(state->surface, &rect, fg_colour);
+			}
+		}
+	}
+	// Draw x pattern (vertical) lines
+	for (int i = 0; i < state->x_pattern_len; ++i) {
+		for (int j = 0; j < state->y_pattern_len; ++j) {
+			if (j % 2 == state->x_pattern[i]) {
+				rect.x = i * state->gap;
+				rect.y = j * state->gap;
+				rect.w = state->line_thickness;
+				rect.h = state->gap;
+				SDL_FillRect(state->surface, &rect, fg_colour);
+			}
+		}
+	}
+	// Join up the lines to avoid leaving holes at the intersections
+	for (int x = state->gap; x < state->output_width; x += state->gap) {
+		for (int y = state->gap; y < state->output_height; y += state->gap) {
+				rect.x = x;
+				rect.y = y;
+				rect.w = state->line_thickness;
+				rect.h = state->line_thickness;
+				SDL_FillRect(state->surface, &rect, fg_colour);
+
+		}
+	}
+
+	SDL_UnlockSurface(state->surface);
+	return Hitomezashi_Draw_Result_Success;
+}