BugFix:

[#20854] PROPERTIES STAMP: Rendering stamp flickers in output renders

Blenfont was not thread safe, that is why one thread can change
the font properties (size, dpi, color, etc) at the same time
that the stamp draw on the image, and then the problem.

To make blenfont thread safe I have to change two important things:

1) Every BLF_* function take one argument, the font id.
2) We have two new function to make font "thread safe":
	BLF_load_unique
	BLF_load_mem_unique

This two function are for case like stamp, that need and own font
that don't share the glyph cache, so can draw without problem
in a different thread.

Why the BLF_*_unique function ?

Because blenfont keep only one copy of a font and keep a list of
"glyph cache". Every glyph cache have size and dpi, so if two
different thread access the same font at the same time, they can
change value and finish with something like the stamp problem.

Why don't remove the glyph cache ?

Because if we do that, we finish with a font object for every size
and dpi, and the stamp is really a special case that happen in
the rendering process, so I really thing is better keep the
glyph cache and make this two new function to handle this
special case.

(When I say "font object" I mean have the same freetype font multiple
times just to have differents size and dpi)

As Matt point we still can have one case that two thread access
the BLF_*_unique function at the same time, but I am looking to
fix this with some class of thread lock.

For now I test and work fine, so if some one found problem, please
let me know.

Campbell I have to change the python api (python/generic/blf_api.c)
to the new syntax, so maybe you can take a look at this.

2 files changed, 70 insertions, 71 deletions

diff --git a/source/blender/blenkernel/intern/image.c b/source/blender/blenkernel/intern/image.c
index 7d194461c78..66e6171d9ee 100644
--- a/source/blender/blenkernel/intern/image.c
+++ b/source/blender/blenkernel/intern/image.c
@@ -1019,17 +1019,17 @@ static void stampdata(Scene *scene, StampData *stamp_data, int do_prefix)
 extern int datatoc_bmonofont_ttf_size;
 extern char datatoc_bmonofont_ttf[];
 
-// XXX - copied from text_font_begin
-void stamp_font_begin(int size)
-{
-	static int mono= -1;
+// XXX - copied from text_font_begin ! Change all the BLF_* here
+static int mono= -1;
 
+int stamp_font_begin(int size)
+{
 	if (mono == -1)
-		mono= BLF_load_mem("monospace", (unsigned char *)datatoc_bmonofont_ttf, datatoc_bmonofont_ttf_size);
+		mono= BLF_load_mem_unique("monospace", (unsigned char *)datatoc_bmonofont_ttf, datatoc_bmonofont_ttf_size);
 
-	BLF_set(mono);
-	BLF_aspect(1.0);
-	BLF_size(size, 72);
+	BLF_aspect(mono, 1.0);
+	BLF_size(mono, size, 72);
+	return(mono); // XXX This is for image_gen.c!!
 }
 
 void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, int height, int channels)
@@ -1049,24 +1049,24 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 
 	stamp_font_begin(scene->r.stamp_font_id);
 
-	BLF_buffer(rectf, rect, width, height, channels);
-	BLF_buffer_col(scene->r.fg_stamp[0], scene->r.fg_stamp[1], scene->r.fg_stamp[2], 1.0);
-	pad= BLF_width("--");
+	BLF_buffer(mono, rectf, rect, width, height, channels);
+	BLF_buffer_col(mono, scene->r.fg_stamp[0], scene->r.fg_stamp[1], scene->r.fg_stamp[2], 1.0);
+	pad= BLF_width(mono, "--");
 
 	x= 0;
 	y= height;
 
 	if (stamp_data.file[0]) {
 		/* Top left corner */
-		BLF_width_and_height(stamp_data.file, &w, &h);
+		BLF_width_and_height(mono, stamp_data.file, &w, &h);
 		y -= h;
 
 		/* also a little of space to the background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y-3, w+3, y+h+3);
 
 		/* and draw the text. */
-		BLF_position(x, y, 0.0);
-		BLF_draw_buffer(stamp_data.file);
+		BLF_position(mono, x, y, 0.0);
+		BLF_draw_buffer(mono, stamp_data.file);
 
 		/* the extra pixel for background. */
 		y -= 4;
@@ -1074,14 +1074,14 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 
 	/* Top left corner, below File */
 	if (stamp_data.note[0]) {
-		BLF_width_and_height(stamp_data.note, &w, &h);
+		BLF_width_and_height(mono, stamp_data.note, &w, &h);
 		y -= h;
 
 		/* and space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, 0, y-2, w+3, y+h+2);
 
-		BLF_position(x, y+1, 0.0);
-		BLF_draw_buffer(stamp_data.note);
+		BLF_position(mono, x, y+1, 0.0);
+		BLF_draw_buffer(mono, stamp_data.note);
 
 		/* the extra pixel for background. */
 		y -= 4;
@@ -1089,14 +1089,14 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 	
 	/* Top left corner, below File (or Note) */
 	if (stamp_data.date[0]) {
-		BLF_width_and_height(stamp_data.date, &w, &h);
+		BLF_width_and_height(mono, stamp_data.date, &w, &h);
 		y -= h;
 
 		/* and space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, 0, y-3, w+3, y+h+3);
 
-		BLF_position(x, y, 0.0);
-		BLF_draw_buffer(stamp_data.date);
+		BLF_position(mono, x, y, 0.0);
+		BLF_draw_buffer(mono, stamp_data.date);
 
 		/* the extra pixel for background. */
 		y -= 4;
@@ -1104,14 +1104,14 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 
 	/* Top left corner, below File, Date or Note */
 	if (stamp_data.rendertime[0]) {
-		BLF_width_and_height(stamp_data.rendertime, &w, &h);
+		BLF_width_and_height(mono, stamp_data.rendertime, &w, &h);
 		y -= h;
 
 		/* and space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, 0, y-3, w+3, y+h+3);
 
-		BLF_position(x, y, 0.0);
-		BLF_draw_buffer(stamp_data.rendertime);
+		BLF_position(mono, x, y, 0.0);
+		BLF_draw_buffer(mono, stamp_data.rendertime);
 	}
 
 	x= 0;
@@ -1119,14 +1119,14 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 
 	/* Bottom left corner, leaving space for timing */
 	if (stamp_data.marker[0]) {
-		BLF_width_and_height(stamp_data.marker, &w, &h);
+		BLF_width_and_height(mono, stamp_data.marker, &w, &h);
 
 		/* extra space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y, w+2, y+h+3);
 
 		/* and pad the text. */
-		BLF_position(x, y+3, 0.0);
-		BLF_draw_buffer(stamp_data.marker);
+		BLF_position(mono, x, y+3, 0.0);
+		BLF_draw_buffer(mono, stamp_data.marker);
 
 		/* space width. */
 		x += w + pad;
@@ -1134,45 +1134,44 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 	
 	/* Left bottom corner */
 	if (stamp_data.time[0]) {
-		BLF_width_and_height(stamp_data.time, &w, &h);
+		BLF_width_and_height(mono, stamp_data.time, &w, &h);
 
 		/* extra space for background */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y, x+w+2, y+h+3);
 
 		/* and pad the text. */
-		BLF_position(x, y+3, 0.0);
-		BLF_draw_buffer(stamp_data.time);
+		BLF_position(mono, x, y+3, 0.0);
+		BLF_draw_buffer(mono, stamp_data.time);
 
 		/* space width. */
 		x += w + pad;
 	}
 	
 	if (stamp_data.frame[0]) {
-		BLF_width_and_height(stamp_data.frame, &w, &h);
+		BLF_width_and_height(mono, stamp_data.frame, &w, &h);
 
 		/* extra space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y, x+w+2, y+h+3);
 
 		/* and pad the text. */
-		BLF_position(x, y+3, 0.0);
-
-		BLF_draw_buffer(stamp_data.frame);
+		BLF_position(mono, x, y+3, 0.0);
+		BLF_draw_buffer(mono, stamp_data.frame);
 
 		/* space width. */
 		x += w + pad;
 	}
 
 	if (stamp_data.camera[0]) {
-		BLF_width_and_height(stamp_data.camera, &w, &h);
+		BLF_width_and_height(mono, stamp_data.camera, &w, &h);
 
 		/* extra space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y, x+w+2, y+h+3);
-		BLF_position(x, y+3, 0.0);
-		BLF_draw_buffer(stamp_data.camera);
+		BLF_position(mono, x, y+3, 0.0);
+		BLF_draw_buffer(mono, stamp_data.camera);
 	}
 	
 	if (stamp_data.scene[0]) {
-		BLF_width_and_height(stamp_data.scene, &w, &h);
+		BLF_width_and_height(mono, stamp_data.scene, &w, &h);
 
 		/* Bottom right corner, with an extra space because blenfont is too strict! */
 		x= width - w - 2;
@@ -1181,12 +1180,12 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y, x+w+3, y+h+3);
 
 		/* and pad the text. */
-		BLF_position(x, y+3, 0.0);
-		BLF_draw_buffer(stamp_data.scene);
+		BLF_position(mono, x, y+3, 0.0);
+		BLF_draw_buffer(mono, stamp_data.scene);
 	}
 	
 	if (stamp_data.strip[0]) {
-		BLF_width_and_height(stamp_data.scene, &w, &h);
+		BLF_width_and_height(mono, stamp_data.scene, &w, &h);
 
 		/* Top right corner, with an extra space because blenfont is too strict! */
 		x= width - w - pad;
@@ -1195,12 +1194,12 @@ void BKE_stamp_buf(Scene *scene, unsigned char *rect, float *rectf, int width, i
 		/* extra space for background. */
 		buf_rectfill_area(rect, rectf, width, height, scene->r.bg_stamp, x, y-3, x+w+pad, y+h+3);
 
-		BLF_position(x, y, 0.0);
-		BLF_draw_buffer(stamp_data.strip);
+		BLF_position(mono, x, y, 0.0);
+		BLF_draw_buffer(mono, stamp_data.strip);
 	}
 
 	/* cleanup the buffer. */
-	BLF_buffer(NULL, NULL, 0, 0, 0);
+	BLF_buffer(mono, NULL, NULL, 0, 0, 0);
 }
 
 void BKE_stamp_info(Scene *scene, struct ImBuf *ibuf)
diff --git a/source/blender/blenkernel/intern/image_gen.c b/source/blender/blenkernel/intern/image_gen.c
index eb256e3775b..9248ce69280 100644
--- a/source/blender/blenkernel/intern/image_gen.c
+++ b/source/blender/blenkernel/intern/image_gen.c
@@ -24,6 +24,7 @@
  */
 
 #include <math.h>
+#include <stdlib.h>
 #include "BLI_math_color.h"
 #include "BLF_api.h"
 
@@ -297,17 +298,17 @@ static void checker_board_grid_fill(unsigned char *rect, float *rect_float, int
 }
 
 /* defined in image.c */
-extern void stamp_font_begin(int size);
+extern int stamp_font_begin(int size);
 
 static void checker_board_text(unsigned char *rect, float *rect_float, int width, int height, int step, int outline)
 {
-	int x, y;
+	int x, y, mono;
 	int pen_x, pen_y;
 	char text[3]= {'A', '1', '\0'};
 
 	/* hard coded size! */
-	stamp_font_begin(54);
-	BLF_buffer(rect_float, rect, width, height, 4);
+	mono= stamp_font_begin(54);
+	BLF_buffer(mono, rect_float, rect, width, height, 4);
     
 	for(y= 0; y < height; y+=step)
 	{
@@ -320,29 +321,29 @@ static void checker_board_text(unsigned char *rect, float *rect_float, int width
 			pen_y = y + 44;
             
 			/* terribly crappy outline font! */
-			BLF_buffer_col(1.0, 1.0, 1.0, 1.0);
-
-			BLF_position(pen_x-outline, pen_y, 0.0);
-			BLF_draw_buffer(text);
-			BLF_position(pen_x+outline, pen_y, 0.0);
-			BLF_draw_buffer(text);
-			BLF_position(pen_x, pen_y-outline, 0.0);
-			BLF_draw_buffer(text);
-			BLF_position(pen_x, pen_y+outline, 0.0);
-			BLF_draw_buffer(text);
+			BLF_buffer_col(mono, 1.0, 1.0, 1.0, 1.0);
+
+			BLF_position(mono, pen_x-outline, pen_y, 0.0);
+			BLF_draw_buffer(mono, text);
+			BLF_position(mono, pen_x+outline, pen_y, 0.0);
+			BLF_draw_buffer(mono, text);
+			BLF_position(mono, pen_x, pen_y-outline, 0.0);
+			BLF_draw_buffer(mono, text);
+			BLF_position(mono, pen_x, pen_y+outline, 0.0);
+			BLF_draw_buffer(mono, text);
             
-			BLF_position(pen_x-outline, pen_y-outline, 0.0);
-			BLF_draw_buffer(text);
-			BLF_position(pen_x+outline, pen_y+outline, 0.0);
-			BLF_draw_buffer(text);
-			BLF_position(pen_x-outline, pen_y+outline, 0.0);
-			BLF_draw_buffer(text);
-			BLF_position(pen_x+outline, pen_y-outline, 0.0);
-			BLF_draw_buffer(text);
-
-			BLF_buffer_col(0.0, 0.0, 0.0, 1.0);
-			BLF_position(pen_x, pen_y, 0.0);
-			BLF_draw_buffer(text);
+			BLF_position(mono, pen_x-outline, pen_y-outline, 0.0);
+			BLF_draw_buffer(mono, text);
+			BLF_position(mono, pen_x+outline, pen_y+outline, 0.0);
+			BLF_draw_buffer(mono, text);
+			BLF_position(mono, pen_x-outline, pen_y+outline, 0.0);
+			BLF_draw_buffer(mono, text);
+			BLF_position(mono, pen_x+outline, pen_y-outline, 0.0);
+			BLF_draw_buffer(mono, text);
+
+			BLF_buffer_col(mono, 0.0, 0.0, 0.0, 1.0);
+			BLF_position(mono, pen_x, pen_y, 0.0);
+			BLF_draw_buffer(mono, text);
             
 			text[1]++;
 		}
@@ -350,8 +351,7 @@ static void checker_board_text(unsigned char *rect, float *rect_float, int width
 	}
     
 	/* cleanup the buffer. */
-	BLF_buffer(0, 0, 0, 0, 0);
-    
+	BLF_buffer(mono, NULL, NULL, 0, 0, 0);
 }
 
 void BKE_image_buf_fill_checker_color(unsigned char *rect, float *rect_float, int width, int height)