Store DPI in floating point instead of deci-integer + implement libfonts_get_output_dpi

Signed-off-by: Mattias Andrée <maandree@kth.se>

3 files changed, 46 insertions, 5 deletions

diff --git a/Makefile b/Makefile
index 2ea54db..dae5d3a 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,8 @@ LIB_NAME = fonts
 
 
 OBJ =\
-	libfonts_calculate_subpixel_order.o
+	libfonts_calculate_subpixel_order.o\
+	libfonts_get_output_dpi.o
 
 HDR =\
 	libfonts.h
diff --git a/libfonts.h b/libfonts.h
index 7f14a48..a31a5e9 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -87,8 +87,8 @@ enum libfonts_orientation {
 };
 
 struct libfonts_rendering_settings {
-	uint16_t deci_dpi_x;
-	uint16_t deci_dpi_y;
+	double dpi_x; /* actually pixels rather than dots */
+	double dpi_y;
 	enum libfonts_antialiasing horizontal_grey_text_antialiasing;
 	enum libfonts_antialiasing vertical_grey_text_antialiasing;
 	enum libfonts_antialiasing diagonal_grey_text_antialiasing;
@@ -107,8 +107,8 @@ struct libfonts_output {
 	int output_screen;
 	enum libfonts_orientation physical_screen_orientation;
 	enum libfonts_subpixel_order unrotated_subpixel_order;
-	uint16_t deci_dpi_x;
-	uint16_t deci_dpi_y;
+	double dpi_x;
+	double dpi_y;
 	struct libfonts_rendering_settings *rendering_settings;
 };
 
diff --git a/libfonts_get_output_dpi.c b/libfonts_get_output_dpi.c
new file mode 100644
index 0000000..259702a
--- /dev/null
+++ b/libfonts_get_output_dpi.c
@@ -0,0 +1,40 @@
+/* See LICENSE file for copyright and license details. */
+#include "libfonts.h"
+#include <ctype.h>
+#include <string.h>
+#include <strings.h>
+
+
+int
+libfonts_get_output_dpi(struct libfonts_output *output, const char *edid)
+{
+	int width, height;
+	char width1, width2, height1, height2;
+
+	output->dpi_x = 0;
+	output->dpi_y = 0;
+	
+	if (strncasecmp(edid, "00""FF""FF""FF""FF""FF""FF""00", 2 * 8) || strlen(edid) < 256)
+		return 0;
+
+	width1 = edid[21 * 2 + 0];
+	width2 = edid[21 * 2 + 0];
+	height1 = edid[22 * 2 + 0];
+	height2 = edid[22 * 2 + 0];
+
+	if (!isxdigit(width1) || !isxdigit(width2) || !isxdigit(height1) || !isxdigit(height2))
+		return 0;
+
+	width  = ((width1  & 15) + (width1  > '9' ? 9 : 0)) << 4;
+	width  |= (width2  & 15) + (width2  > '9' ? 9 : 0);
+	height = ((height1 & 15) + (height1 > '9' ? 9 : 0)) << 4;
+	height |= (height2 & 15) + (height2 > '9' ? 9 : 0);
+
+	if (!width || !height)
+		return 0;
+
+	output->dpi_x = (double)output->output_width  / (double)width  * 2.54;
+	output->dpi_y = (double)output->output_height / (double)height * 2.54;
+
+	return 1;
+}