BLF: Add Batching capabilities.

You can now use BLF_batching_start and BLF_batching_end to batch every
drawcall to BLF together minimizing the overhead introduced by BLF and the
opengl driver.

These calls cannot be nested (for now).

If the modelview matrix changes, previously batched calls are issued and a
the process resume with the new matrix.

However the projection matrix MUST not change and gl scissors as well.

1 files changed, 54 insertions, 9 deletions

diff --git a/source/blender/blenfont/intern/blf_font.c b/source/blender/blenfont/intern/blf_font.c
index 868d8eb775e..1df1dc5706c 100644
--- a/source/blender/blenfont/intern/blf_font.c
+++ b/source/blender/blenfont/intern/blf_font.c
@@ -97,6 +97,11 @@ static void blf_batching_init(void)
 	g_batch.verts = GWN_vertbuf_create_with_format_ex(&format, GWN_USAGE_STREAM);
 	GWN_vertbuf_data_alloc(g_batch.verts, BLF_BATCHING_SIZE);
 
+	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.pos_loc, &g_batch.pos_step);
+	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.tex_loc, &g_batch.tex_step);
+	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.col_loc, &g_batch.col_step);
+	g_batch.glyph_ct = 0;
+
 	g_batch.batch = GWN_batch_create_ex(GWN_PRIM_POINTS, g_batch.verts, NULL, GWN_BATCH_OWNS_VBO);
 }
 
@@ -118,17 +123,53 @@ void blf_batching_start(FontBLF *font)
 		blf_batching_init();
 	}
 
-	zero_v2(g_batch.ofs);
-	if ((font->flags & (BLF_ROTATION | BLF_MATRIX | BLF_ASPECT)) == 0) {
+	const bool font_changed = (g_batch.font != font);
+	g_batch.font = font;
+
+	const bool manual_ofs_active = ((font->flags & (BLF_ROTATION | BLF_MATRIX | BLF_ASPECT)) == 0);
+	g_batch.active = g_batch.enabled && manual_ofs_active;
+
+	if (manual_ofs_active) {
+		/* Offset is applied to each glyph. */
 		copy_v2_v2(g_batch.ofs, font->pos);
 	}
+	else {
+		/* Offset is baked in modelview mat. */
+		zero_v2(g_batch.ofs);
+	}
 
-	/* restart to 1st vertex data pointers */
-	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.pos_loc, &g_batch.pos_step);
-	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.tex_loc, &g_batch.tex_step);
-	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.col_loc, &g_batch.col_step);
-	g_batch.glyph_ct = 0;
-	g_batch.font = font;
+	if (g_batch.active) {
+		float gpumat[4][4];
+		gpuGetModelViewMatrix(gpumat);
+
+		bool mat_changed = (memcmp(gpumat, g_batch.mat, sizeof(g_batch.mat)) != 0);
+		/* Save for next memcmp. */
+		memcpy(g_batch.mat, gpumat, sizeof(g_batch.mat));
+
+		if (mat_changed) {
+			/* Modelviewmat is no longer the same.
+			 * Flush cache but with the previous mat. */
+			gpuPushMatrix();
+			gpuLoadMatrix(g_batch.mat);
+		}
+
+		/* flush cache if config is not the same. */
+		if (mat_changed || font_changed) {
+			blf_batching_draw();
+		}
+		else {
+			/* Nothing changed continue batching. */
+			return;
+		}
+
+		if (mat_changed) {
+			gpuPopMatrix();
+		}
+	}
+	else {
+		/* flush cache */
+		blf_batching_draw();
+	}
 }
 
 void blf_batching_draw(void)
@@ -152,12 +193,16 @@ void blf_batching_draw(void)
 
 	glDisable(GL_BLEND);
 
+	/* restart to 1st vertex data pointers */
+	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.pos_loc, &g_batch.pos_step);
+	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.tex_loc, &g_batch.tex_step);
+	GWN_vertbuf_attr_get_raw_data(g_batch.verts, g_batch.col_loc, &g_batch.col_step);
 	g_batch.glyph_ct = 0;
 }
 
 static void blf_batching_end(void)
 {
-	if (!g_batch.enabled) {
+	if (!g_batch.active) {
 		blf_batching_draw();
 	}
 }