<div style="color:black;font: 10pt arial;"> <div> Hi Johann, Have you tested on another back end? If so, are the results different? I gave it a try and got similar results. cairo_scaled_font_create() says "Creates a cairo_scaled_font_t object from a font face and matrices that describe the size of the font and the environment in which it will be used." Then cairo_set_scaled_font() says "the current CTM of the cairo_t should be the same as that of the cairo_scaled_font_t, which can be accessed using cairo_scaled_font_get_ctm()." It sounds like you should get the ctm from the cairo_scaled_font_t pointer and this does work. It is confusing though when you don't get a ctm back with a cairo_set_scaled_font()/cairo_get_scaled_font() pair. Seems like a bug to me. Eric </div> <div> </div> <div> /* Test a scaled font. A problem getting the scaled font ctm back with a cairo_set_scaled_font() cairo_get_scaled_font() pair. gcc -Wall -g font_scale1.c -o font_scale1 -I/usr/include/freetype2 `pkg-config --cflags --libs cairo fontconfig` -lfreetype Tested on Ubuntu18.04 */ #include<cairo.h> #include<cairo-ft.h> #include<stdio.h> #include<ft2build.h> #include FT_FREETYPE_H #include<fontconfig/fontconfig.h> static double width=500.0; static double height=500.0; static void draw_font(cairo_t *cr, double scale_ctm_x, double scale_ctm_y, cairo_scaled_font_t *sf); int main() { //Starting font. char *font="/usr/share/fonts/truetype/freefont/FreeSansBold.ttf"; FT_Error error; FT_Library library; FT_Face face; error=FT_Init_FreeType(&library); if(error) printf("Init_FreeType Error\n"); error=FT_New_Face(library, font, 0, &face); if(error==FT_Err_Ok) printf("New font face.\n"); else printf("Cannot open font.\n"); cairo_surface_t *surface=cairo_image_surface_create(CAIRO_FORMAT_ARGB32, width, height); cairo_t *cr=cairo_create(surface); //Paint the background. cairo_set_source_rgba(cr, 1.0, 1.0, 1.0, 1.0); cairo_paint(cr); //Cartesian coordinates. cairo_set_source_rgba(cr, 0.0, 0.0, 0.0, 1.0); cairo_move_to(cr, 0.0, height/2.0); cairo_line_to(cr, width, height/2.0); cairo_stroke(cr); cairo_move_to(cr, width/2.0, 0.0); cairo_line_to(cr, width/2.0, height); cairo_stroke(cr); //Test changing the scale values for the scaled font. cairo_matrix_t fm, cm, sm; double scale_ctm_x=1.5; double scale_ctm_y=1.5; cairo_matrix_init_scale(&fm, 30.0, 30.0); cairo_matrix_init_scale(&cm, scale_ctm_x, scale_ctm_y); cairo_font_options_t *fo=cairo_font_options_create(); cairo_font_face_t *ff=cairo_ft_font_face_create_for_ft_face(face, 0); cairo_scaled_font_t *sf=cairo_scaled_font_create(ff, &fm, &cm, fo); //Draw the scaled font. cairo_save(cr); cairo_translate(cr, width/2.0, height/2.0); cairo_set_scaled_font(cr, sf); cairo_transform(cr, &cm); cairo_set_source_rgba(cr, 0.0, 0.0, 1.0, 1.0); cairo_text_extents_t ex; cairo_text_extents(cr, "Scaled Font", &ex); cairo_move_to(cr, -0.5*ex.width, 0.0); cairo_show_text(cr, "Scaled Font"); cairo_restore(cr); //Look at the matrices. printf("font matrix1 %f %f %f %f %f %f\n", fm.xx, fm.xy, fm.x0, fm.yx, fm.yy, fm.y0); printf("current matrix2 %f %f %f %f %f %f\n", cm.xx, cm.xy, cm.x0, cm.yx, cm.yy, cm.y0); cairo_matrix_multiply(&sm, &fm, &cm); printf("scale matrix3 %f %f %f %f %f %f\n", sm.xx, sm.xy, sm.x0, sm.yx, sm.yy, sm.y0); //Draw some extra text. draw_font(cr, scale_ctm_x, scale_ctm_y, sf); //Output the results. printf("Output to font_scale1.png\n"); cairo_surface_write_to_png(surface, "font_scale1.png"); //Clean up. cairo_font_options_destroy(fo); cairo_font_face_destroy(ff); cairo_scaled_font_destroy(sf); cairo_destroy(cr); cairo_surface_destroy(surface); if(face!=NULL) FT_Done_Face(face); if(library!=NULL) FT_Done_FreeType(library); //Clear some caches for valgrind. cairo_debug_reset_static_data(); FcFini(); return 0; } static void draw_font(cairo_t *cr, double scale_ctm_x, double scale_ctm_y, cairo_scaled_font_t *sf) { //Use sf pointer to get the matrices. cairo_matrix_t fm, cm, sm; cairo_scaled_font_get_font_matrix(sf, &fm); cairo_scaled_font_get_ctm(sf, &cm); cairo_scaled_font_get_scale_matrix(sf, &sm); printf("font matrix2 %f %f %f %f %f %f\n", fm.xx, fm.xy, fm.x0, fm.yx, fm.yy, fm.y0); printf("current matrix2 %f %f %f %f %f %f\n", cm.xx, cm.xy, cm.x0, cm.yx, cm.yy, cm.y0); printf("scale matrix2 %f %f %f %f %f %f\n", sm.xx, sm.xy, sm.x0, sm.yx, sm.yy, sm.y0); cairo_save(cr); cairo_text_extents_t ex; cairo_translate(cr, width/2.0, height/2.0); cairo_set_scaled_font(cr, sf); cairo_transform(cr, &cm); cairo_set_source_rgba(cr, 0.0, 1.0, 0.0, 1.0); cairo_text_extents(cr, "Scaled Font", &ex); cairo_move_to(cr, -0.5*ex.width, ex.height); cairo_show_text(cr, "Scaled Font"); cairo_restore(cr); //Set the scaled font and then get it back. This doesn't get the scaled font ctm. cairo_set_scaled_font(cr, sf); cairo_scaled_font_t* sf2=cairo_get_scaled_font(cr); cairo_scaled_font_get_font_matrix(sf2, &fm); cairo_scaled_font_get_ctm(sf2, &cm); cairo_scaled_font_get_scale_matrix(sf2, &sm); printf("font matrix3 %f %f %f %f %f %f\n", fm.xx, fm.xy, fm.x0, fm.yx, fm.yy, fm.y0); printf("current matrix3 %f %f %f %f %f %f\n", cm.xx, cm.xy, cm.x0, cm.yx, cm.yy, cm.y0); printf("scale matrix3 %f %f %f %f %f %f\n", sm.xx, sm.xy, sm.x0, sm.yx, sm.yy, sm.y0); cairo_translate(cr, width/2.0, height/2.0); cairo_set_scaled_font(cr, sf); cairo_transform(cr, &cm); cairo_set_source_rgba(cr, 1.0, 0.0, 0.0, 1.0); cairo_text_extents(cr, "Scaled Font", &ex); cairo_move_to(cr, -0.5*ex.width, 3.0*ex.height); cairo_show_text(cr, "Scaled Font"); } </div> <div> </div> </div>