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- /*
- u8g22_polygon.c
- */
- #include "u8g2.h"
- /*===========================================*/
- /* local definitions */
- typedef int16_t pg_word_t;
- struct pg_point_struct
- {
- pg_word_t x;
- pg_word_t y;
- };
- typedef struct _pg_struct pg_struct; /* forward declaration */
- struct pg_edge_struct
- {
- pg_word_t x_direction; /* 1, if x2 is greater than x1, -1 otherwise */
- pg_word_t height;
- pg_word_t current_x_offset;
- pg_word_t error_offset;
-
- /* --- line loop --- */
- pg_word_t current_y;
- pg_word_t max_y;
- pg_word_t current_x;
- pg_word_t error;
- /* --- outer loop --- */
- uint8_t (*next_idx_fn)(pg_struct *pg, uint8_t i);
- uint8_t curr_idx;
- };
- /* maximum number of points in the polygon */
- /* can be redefined, but highest possible value is 254 */
- #define PG_MAX_POINTS 6
- /* index numbers for the pge structures below */
- #define PG_LEFT 0
- #define PG_RIGHT 1
- struct _pg_struct
- {
- struct pg_point_struct list[PG_MAX_POINTS];
- uint8_t cnt;
- uint8_t is_min_y_not_flat;
- pg_word_t total_scan_line_cnt;
- struct pg_edge_struct pge[2]; /* left and right line draw structures */
- };
- /*===========================================*/
- /* procedures, which should not be inlined (save as much flash ROM as possible */
- #define PG_NOINLINE U8G2_NOINLINE
- static uint8_t pge_Next(struct pg_edge_struct *pge) PG_NOINLINE;
- static uint8_t pg_inc(pg_struct *pg, uint8_t i) PG_NOINLINE;
- static uint8_t pg_dec(pg_struct *pg, uint8_t i) PG_NOINLINE;
- static void pg_expand_min_y(pg_struct *pg, pg_word_t min_y, uint8_t pge_idx) PG_NOINLINE;
- static void pg_line_init(pg_struct * const pg, uint8_t pge_index) PG_NOINLINE;
- /*===========================================*/
- /* line draw algorithm */
- static uint8_t pge_Next(struct pg_edge_struct *pge)
- {
- if ( pge->current_y >= pge->max_y )
- return 0;
-
- pge->current_x += pge->current_x_offset;
- pge->error += pge->error_offset;
- if ( pge->error > 0 )
- {
- pge->current_x += pge->x_direction;
- pge->error -= pge->height;
- }
-
- pge->current_y++;
- return 1;
- }
- /* assumes y2 > y1 */
- static void pge_Init(struct pg_edge_struct *pge, pg_word_t x1, pg_word_t y1, pg_word_t x2, pg_word_t y2)
- {
- pg_word_t dx = x2 - x1;
- pg_word_t width;
- pge->height = y2 - y1;
- pge->max_y = y2;
- pge->current_y = y1;
- pge->current_x = x1;
- if ( dx >= 0 )
- {
- pge->x_direction = 1;
- width = dx;
- pge->error = 0;
- }
- else
- {
- pge->x_direction = -1;
- width = -dx;
- pge->error = 1 - pge->height;
- }
-
- pge->current_x_offset = dx / pge->height;
- pge->error_offset = width % pge->height;
- }
- /*===========================================*/
- /* convex polygon algorithm */
- static uint8_t pg_inc(pg_struct *pg, uint8_t i)
- {
- i++;
- if ( i >= pg->cnt )
- i = 0;
- return i;
- }
- static uint8_t pg_dec(pg_struct *pg, uint8_t i)
- {
- i--;
- if ( i >= pg->cnt )
- i = pg->cnt-1;
- return i;
- }
- static void pg_expand_min_y(pg_struct *pg, pg_word_t min_y, uint8_t pge_idx)
- {
- uint8_t i = pg->pge[pge_idx].curr_idx;
- for(;;)
- {
- i = pg->pge[pge_idx].next_idx_fn(pg, i);
- if ( pg->list[i].y != min_y )
- break;
- pg->pge[pge_idx].curr_idx = i;
- }
- }
- static uint8_t pg_prepare(pg_struct *pg)
- {
- pg_word_t max_y;
- pg_word_t min_y;
- uint8_t i;
- /* setup the next index procedures */
- pg->pge[PG_RIGHT].next_idx_fn = pg_inc;
- pg->pge[PG_LEFT].next_idx_fn = pg_dec;
-
- /* search for highest and lowest point */
- max_y = pg->list[0].y;
- min_y = pg->list[0].y;
- pg->pge[PG_LEFT].curr_idx = 0;
- for( i = 1; i < pg->cnt; i++ )
- {
- if ( max_y < pg->list[i].y )
- {
- max_y = pg->list[i].y;
- }
- if ( min_y > pg->list[i].y )
- {
- pg->pge[PG_LEFT].curr_idx = i;
- min_y = pg->list[i].y;
- }
- }
- /* calculate total number of scan lines */
- pg->total_scan_line_cnt = max_y;
- pg->total_scan_line_cnt -= min_y;
-
- /* exit if polygon height is zero */
- if ( pg->total_scan_line_cnt == 0 )
- return 0;
-
- /* if the minimum y side is flat, try to find the lowest and highest x points */
- pg->pge[PG_RIGHT].curr_idx = pg->pge[PG_LEFT].curr_idx;
- pg_expand_min_y(pg, min_y, PG_RIGHT);
- pg_expand_min_y(pg, min_y, PG_LEFT);
-
- /* check if the min side is really flat (depends on the x values) */
- pg->is_min_y_not_flat = 1;
- if ( pg->list[pg->pge[PG_LEFT].curr_idx].x != pg->list[pg->pge[PG_RIGHT].curr_idx].x )
- {
- pg->is_min_y_not_flat = 0;
- }
- else
- {
- pg->total_scan_line_cnt--;
- if ( pg->total_scan_line_cnt == 0 )
- return 0;
- }
- return 1;
- }
- static void pg_hline(pg_struct *pg, u8g2_t *u8g2)
- {
- pg_word_t x1, x2, y;
- x1 = pg->pge[PG_LEFT].current_x;
- x2 = pg->pge[PG_RIGHT].current_x;
- y = pg->pge[PG_RIGHT].current_y;
-
- if ( y < 0 )
- return;
- if ( y >= u8g2_GetDisplayHeight(u8g2) ) // does not work for 256x64 display???
- return;
- if ( x1 < x2 )
- {
- if ( x2 < 0 )
- return;
- if ( x1 >= u8g2_GetDisplayWidth(u8g2) )
- return;
- if ( x1 < 0 )
- x1 = 0;
- if ( x2 >= u8g2_GetDisplayWidth(u8g2) )
- x2 = u8g2_GetDisplayWidth(u8g2);
- u8g2_DrawHLine(u8g2, x1, y, x2 - x1);
- }
- else
- {
- if ( x1 < 0 )
- return;
- if ( x2 >= u8g2_GetDisplayWidth(u8g2) )
- return;
- if ( x2 < 0 )
- x1 = 0;
- if ( x1 >= u8g2_GetDisplayWidth(u8g2) )
- x1 = u8g2_GetDisplayWidth(u8g2);
- u8g2_DrawHLine(u8g2, x2, y, x1 - x2);
- }
- }
- static void pg_line_init(pg_struct * const pg, uint8_t pge_index)
- {
- struct pg_edge_struct *pge = pg->pge+pge_index;
- uint8_t idx;
- pg_word_t x1;
- pg_word_t y1;
- pg_word_t x2;
- pg_word_t y2;
- idx = pge->curr_idx;
- y1 = pg->list[idx].y;
- x1 = pg->list[idx].x;
- idx = pge->next_idx_fn(pg, idx);
- y2 = pg->list[idx].y;
- x2 = pg->list[idx].x;
- pge->curr_idx = idx;
-
- pge_Init(pge, x1, y1, x2, y2);
- }
- static void pg_exec(pg_struct *pg, u8g2_t *u8g2)
- {
- pg_word_t i = pg->total_scan_line_cnt;
- /* first line is skipped if the min y line is not flat */
- pg_line_init(pg, PG_LEFT);
- pg_line_init(pg, PG_RIGHT);
-
- if ( pg->is_min_y_not_flat != 0 )
- {
- pge_Next(&(pg->pge[PG_LEFT]));
- pge_Next(&(pg->pge[PG_RIGHT]));
- }
- do
- {
- pg_hline(pg, u8g2);
- while ( pge_Next(&(pg->pge[PG_LEFT])) == 0 )
- {
- pg_line_init(pg, PG_LEFT);
- }
- while ( pge_Next(&(pg->pge[PG_RIGHT])) == 0 )
- {
- pg_line_init(pg, PG_RIGHT);
- }
- i--;
- } while( i > 0 );
- }
- /*===========================================*/
- /* API procedures */
- static void pg_ClearPolygonXY(pg_struct *pg)
- {
- pg->cnt = 0;
- }
- static void pg_AddPolygonXY(pg_struct *pg, int16_t x, int16_t y)
- {
- if ( pg->cnt < PG_MAX_POINTS )
- {
- pg->list[pg->cnt].x = x;
- pg->list[pg->cnt].y = y;
- pg->cnt++;
- }
- }
- static void pg_DrawPolygon(pg_struct *pg, u8g2_t *u8g2)
- {
- if ( pg_prepare(pg) == 0 )
- return;
- pg_exec(pg, u8g2);
- }
- pg_struct u8g2_pg;
- void u8g2_ClearPolygonXY(void)
- {
- pg_ClearPolygonXY(&u8g2_pg);
- }
- void u8g2_AddPolygonXY(U8X8_UNUSED u8g2_t *u8g2, int16_t x, int16_t y)
- {
- pg_AddPolygonXY(&u8g2_pg, x, y);
- }
- void u8g2_DrawPolygon(u8g2_t *u8g2)
- {
- pg_DrawPolygon(&u8g2_pg, u8g2);
- }
- void u8g2_DrawTriangle(u8g2_t *u8g2, int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2)
- {
- u8g2_ClearPolygonXY();
- u8g2_AddPolygonXY(u8g2, x0, y0);
- u8g2_AddPolygonXY(u8g2, x1, y1);
- u8g2_AddPolygonXY(u8g2, x2, y2);
- u8g2_DrawPolygon(u8g2);
- }
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