Font preview for file browser

D1002 by @plasmasolutions, with own refactoring.

Note, needed to do a bad-level call here (IMB -> BLF)
Also can't use the BLF API directly because its not thread-safe.
So keep the function isolated (blf_thumbs.c).

3 files changed, 111 insertions, 0 deletions

diff --git a/source/blender/blenfont/BLF_api.h b/source/blender/blenfont/BLF_api.h
index 206345582b2..09734bd9754 100644
--- a/source/blender/blenfont/BLF_api.h
+++ b/source/blender/blenfont/BLF_api.h
@@ -186,6 +186,12 @@ char **BLF_dir_get(int *ndir) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
 /* Free the data return by BLF_dir_get. */
 void BLF_dir_free(char **dirs, int count) ATTR_NONNULL();
 
+/* blf_thumbs.c */
+void BLF_thumb_preview(
+        const char *filename, const char **draw_str, const unsigned char draw_str_lines,
+        const float font_color[4], const int font_size,
+        unsigned char *buf, int w, int h, int channels) ATTR_NONNULL();
+
 #ifdef DEBUG
 void BLF_state_print(int fontid);
 #endif
diff --git a/source/blender/blenfont/CMakeLists.txt b/source/blender/blenfont/CMakeLists.txt
index 392a9ede100..2f10c3580e0 100644
--- a/source/blender/blenfont/CMakeLists.txt
+++ b/source/blender/blenfont/CMakeLists.txt
@@ -47,6 +47,7 @@ set(SRC
 	intern/blf_font.c
 	intern/blf_glyph.c
 	intern/blf_lang.c
+	intern/blf_thumbs.c
 	intern/blf_translation.c
 	intern/blf_util.c
 
diff --git a/source/blender/blenfont/intern/blf_thumbs.c b/source/blender/blenfont/intern/blf_thumbs.c
new file mode 100644
index 00000000000..afda6a382f9
--- /dev/null
+++ b/source/blender/blenfont/intern/blf_thumbs.c
@@ -0,0 +1,104 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Contributor(s): Thomas Beck
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/blenfont/intern/blf_thumbs.c
+ *  \ingroup blf
+ *
+ * Utility function to generate font preview images.
+ *
+ * Isolate since this needs to be called by #ImBuf code (bad level call).
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <ft2build.h>
+
+#include FT_FREETYPE_H
+
+#include "BLI_utildefines.h"
+#include "BLI_listbase.h"
+#include "BLI_rect.h"
+#include "BLI_threads.h"
+
+#include "blf_internal.h"
+#include "blf_internal_types.h"
+
+#include "BLF_api.h"
+
+#include "BLI_strict_flags.h"
+
+/**
+ * This function is used for generating thumbnail previews.
+ *
+ * \note called from a thread, so it bypasses the normal BLF_* api (which isn't thread-safe).
+ */
+void BLF_thumb_preview(
+        const char *filename,
+        const char **draw_str, const unsigned char draw_str_lines,
+        const float font_color[4], const int font_size,
+        unsigned char *buf, int w, int h, int channels)
+{
+	const unsigned int dpi = 72;
+	const int font_size_min = 6;
+	int font_size_curr;
+	/* shrink 1/th each line */
+	int font_shrink = 4;
+
+	FontBLF* font;
+	int i;
+
+	/* Create a new blender font obj and fill it with default values */
+	font = blf_font_new("thumb_font", filename);
+	if (!font) {
+		printf("Info: Can't load font '%s', no preview possible\n", filename);
+		return;
+	}
+
+	/* Would be done via the BLF API, but we're not using a fontid here */
+	font->buf_info.cbuf = buf;
+	font->buf_info.ch = channels;
+	font->buf_info.w = w;
+	font->buf_info.h = h;
+
+	/* Always create the image with a white font,
+	 * the caller can theme how it likes */
+	memcpy(font->buf_info.col, font_color, sizeof(font->buf_info.col));
+	font->pos[1] = (float)h;
+
+	font_size_curr = font_size;
+
+	for (i = 0; i < draw_str_lines; i++) {
+		blf_font_size(font, (unsigned int)MAX2(font_size_min, font_size_curr), dpi);
+
+		/* decrease font size each time */
+		font_size_curr -= (font_size_curr / font_shrink);
+		font_shrink += 1;
+
+		font->pos[1] -= font->glyph_cache->ascender * 1.1f;
+
+		blf_font_buffer(font, draw_str[i]);
+	}
+
+	blf_font_free(font);
+}