text drawing artifact

[Carl Worth]

Steven,

Can you describe what you're seeing and what you're expecting to see?

Or show images of the good and bad results?

I compiled and ran your code, with and without the change you suggested,
and saw the same result in both cases, (or else I missed something).

So I'm not clear if I'm just not getting the same behavior you are, or
if I'm not seeing something.

-Carl

On Wed, May 29 2024, Steven J. Abner wrote:
>  I've gotten frustrated and need help. I've tried different combos of 
> matrix, cairo_t, clip
> and saves. I just can't make this work: draw text then drawing. Can 
> switch order:
> drawing then draw text to make it work, but in creating objects parsing 
> order for draw
> events is not really an option.
>  What am I doing wrong?????
>
> demo: compile
>  gcc -x c -std=c99 -pipe -fno-builtin -fmessage-length=0 -g `pkg-config 
> --cflags gtk+-3.0` -o a artifact.c `pkg-config --libs gtk+-3.0`
> demo: run
>  ./a
> then try altering draw() so draw_wmgr() runs before text drawing code 
> to see difference.
>   Steve
>
> //gcc -x c -std=c99 -pipe -fno-builtin -fmessage-length=0 -g `pkg-config --cflags gtk+-3.0` -o a artifact.c `pkg-config --libs gtk+-3.0`
> #ifndef M_PI
>  #define M_PI 3.14159265358979323846
> #endif
> #include <gtk/gtk.h>
>
> typedef struct _PhxObject              PhxObject;
> typedef struct { int x, y, w, h; }     PhxRectangle;
> struct _PhxObject {
>  PhxRectangle      mete_box;        /* allocate box */
>  PhxRectangle      draw_box;        /* clip box */
> };
>
> static void
> draw_wmgr(PhxObject *b, cairo_t *cr) {
>
>   cairo_save(cr);
>
>   double bottom = b->mete_box.y + b->draw_box.y + b->draw_box.h;
>   double top = b->mete_box.y + b->draw_box.y;
>   double radius = b->draw_box.h / 2;
>   double xc = b->mete_box.x + b->draw_box.x + (b->draw_box.w / 2);
>   double yc = b->mete_box.y + b->draw_box.y + (b->draw_box.h / 2);
>
>   cairo_arc(cr, xc, yc, radius, 0, M_PI * 2);
>   cairo_clip_preserve(cr);
>
>   cairo_matrix_t matrix;
>   cairo_pattern_t *r1;
>   cairo_get_matrix(cr, &matrix);
>     // fill in circle
>   cairo_translate(cr, xc, bottom + 6.5);
>   cairo_scale(cr, 1, 0.7);
>   cairo_translate(cr, -xc, -(bottom + 6.5));
>   r1 = cairo_pattern_create_radial(xc, yc, 6,
>                                    xc, yc, (double)(b->draw_box.h + 8.5));
>   cairo_pattern_add_color_stop_rgba(r1, 0, .7, .7, 1, 1);
>   cairo_pattern_add_color_stop_rgba(r1, 1, 0, 0, .4, 1);
>   cairo_set_source(cr, r1);
>   cairo_fill_preserve(cr);
>   cairo_pattern_destroy(r1);
>
>   cairo_set_matrix(cr, &matrix);
>
>   r1 = cairo_pattern_create_radial(xc - 0.7, top + 3.5, .4,
>                                    xc - 0.7, top + 3.5, 8);
>   cairo_pattern_add_color_stop_rgba(r1, 0, .8, .8, 1, 1);
>   cairo_pattern_add_color_stop_rgba(r1, 1, .4, .4, 1, .05);
>   cairo_set_source(cr, r1);
>   cairo_fill_preserve(cr);
>   cairo_pattern_destroy(r1);
>
>   cairo_set_source_rgba(cr, 0, 0, 0, 1);
>   cairo_set_line_width(cr, .5);
>   cairo_stroke(cr);
>
>   cairo_restore(cr);
> }
>
> static _Bool
> draw(void *widget, cairo_t *cr) {
>
>   cairo_save(cr);
>   cairo_select_font_face(cr, "DejaVu Sans", 0, 0);
>   cairo_set_font_size(cr, 9.5);
>   cairo_rectangle(cr, 108, 7, 8, 12);
>   cairo_clip(cr);
>
>   cairo_set_source_rgba(cr, 0, 0, 0, 1);
>   cairo_move_to(cr, 108, 7 + 9);
>   cairo_show_text(cr, "O");
>   cairo_restore(cr);
>
>   PhxObject b = { {554, 5, 14, 14}, {0, 0, 14, 14} };
>   draw_wmgr(&b, cr);
>
> }
>
> int
> main(int argc, char *argv[]) {
>
>   gtk_init(&argc, &argv); // initialize Gdk
>
>   int window_width = 576;
>   int window_height = 200;
>
>   GtkWidget *main_window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
>   GtkWindow *window = GTK_WINDOW(main_window);
>   gtk_window_set_default_size(window, window_width, window_height);
>   gtk_window_set_decorated(GTK_WINDOW(window), FALSE);
>   gtk_widget_realize(main_window);
>
>   g_signal_connect(G_OBJECT(main_window), "delete-event",
>                                 G_CALLBACK(gtk_main_quit), NULL);
>
>   GtkWidget *box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
>   gtk_container_add(GTK_CONTAINER(main_window), box);
>
>   GtkWidget *da = gtk_drawing_area_new();
>   gtk_box_pack_start((GtkBox*)box, da, TRUE, TRUE, 0);
>   gtk_widget_realize(da);
>
>   g_signal_connect(G_OBJECT(da), "draw", G_CALLBACK(draw), NULL);
>
>   gtk_widget_show_all(main_window);
>   gtk_main();
>   return EXIT_SUCCESS;
> }