Python/UI: add more convenient API for drawing based on DPI.

system.ui_scale: size multiplier to use when drawing custom UI elements.
system.ui_line_width: suggested line thickness and point size in pixels.

4 files changed, 25 insertions, 15 deletions

diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index 9f41f9175c4..7fd48ce081c 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -230,7 +230,7 @@ enum {
 
 /* scale fixed button widths by this to account for DPI */
 
-#define UI_DPI_FAC ((U.pixelsize * (float)U.dpi) / 72.0f)
+#define UI_DPI_FAC (U.dpi_fac)
 /* 16 to copy ICON_DEFAULT_HEIGHT */
 #define UI_DPI_ICON_SIZE ((float)16 * UI_DPI_FAC)
 
diff --git a/source/blender/makesdna/DNA_userdef_types.h b/source/blender/makesdna/DNA_userdef_types.h
index 7b2ad060e61..88cbd848387 100644
--- a/source/blender/makesdna/DNA_userdef_types.h
+++ b/source/blender/makesdna/DNA_userdef_types.h
@@ -487,12 +487,16 @@ typedef struct UserDef {
 	int audioformat;
 	int audiochannels;
 
+	float ui_scale;     /* setting for UI scale */
+	int ui_line_width;  /* setting for UI line width */
+	int dpi;            /* runtime, full DPI divided by pixelsize */
+	float dpi_fac;      /* runtime, multiplier to scale UI elements based on DPI */
+	float pixelsize;	/* runtime, line width and point size based on DPI */
+	int virtual_pixel;	/* deprecated, for forward compatibility */
+
 	int scrollback;     /* console scrollback limit */
-	int dpi;            /* range 48-128? */
-	float ui_scale;     /* interface scale */
-	int ui_line_width;  /* interface line width */
 	char node_margin;   /* node insert offset (aka auto-offset) margin, but might be useful for later stuff as well */
-	char pad2;
+	char pad2[5];
 	short transopts;    /* eUserpref_Translation_Flags */
 	short menuthreshold1, menuthreshold2;
 
@@ -583,8 +587,6 @@ typedef struct UserDef {
 	int compute_device_id;
 	
 	float fcu_inactive_alpha;	/* opacity of inactive F-Curves in F-Curve Editor */
-	float pixelsize;			/* private, set by GHOST, to multiply DPI with */
-	int virtual_pixel;			/* virtual pixelsize mode */
 
 	short pie_interaction_type;     /* if keeping a pie menu spawn button pressed after this time, it turns into
 	                             * a drag/release pie menu */
diff --git a/source/blender/makesrna/intern/rna_userdef.c b/source/blender/makesrna/intern/rna_userdef.c
index 03034522d30..c50d09746ad 100644
--- a/source/blender/makesrna/intern/rna_userdef.c
+++ b/source/blender/makesrna/intern/rna_userdef.c
@@ -3957,20 +3957,27 @@ static void rna_def_userdef_system(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "International Fonts", "Use international fonts");
 	RNA_def_property_update(prop, NC_WINDOW, "rna_userdef_language_update");
 
+	prop = RNA_def_property(srna, "ui_scale", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+	RNA_def_property_float_sdna(prop, NULL, "dpi_fac");
+	RNA_def_property_ui_text(prop, "UI Scale",
+	                         "Size multiplier to use when drawing custom user interface elements, so that "
+	                         "they are scaled correctly on screens with different DPI. This value is based "
+	                         "on operating system DPI settings and Blender display scale");
+
+	prop = RNA_def_property(srna, "ui_line_width", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+	RNA_def_property_float_sdna(prop, NULL, "pixelsize");
+	RNA_def_property_ui_text(prop, "UI Line Width",
+	                         "Suggested line thickness and point size in pixels, for add-ons drawing custom "
+	                         "user interface elements, based on operating system settings and Blender UI scale");
+
 	prop = RNA_def_property(srna, "dpi", PROP_INT, PROP_NONE);
 	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-	RNA_def_property_ui_text(prop, "DPI",
-	                         "DPI for add-ons to use when drawing custom user interface elements, controlled by "
-	                         "operating system settings and Blender UI scale, with a reference value of 72 DPI "
-	                         "(note that since this value includes a user defined scale, it is not always the "
-	                         "actual monitor DPI)");
 
 	prop = RNA_def_property(srna, "pixel_size", PROP_FLOAT, PROP_NONE);
 	RNA_def_property_clear_flag(prop, PROP_EDITABLE);
 	RNA_def_property_float_sdna(prop, NULL, "pixelsize");
-	RNA_def_property_ui_text(prop, "Pixel Size",
-	                         "Suggested line thickness and point size in pixels, for add-ons drawing custom user "
-	                         "interface elements, controlled by operating system settings and Blender UI scale");
 
 	prop = RNA_def_property(srna, "font_path_ui", PROP_STRING, PROP_FILEPATH);
 	RNA_def_property_string_sdna(prop, NULL, "font_path_ui");
diff --git a/source/blender/windowmanager/intern/wm_window.c b/source/blender/windowmanager/intern/wm_window.c
index e0a1f0f14ad..2d94cc1dae7 100644
--- a/source/blender/windowmanager/intern/wm_window.c
+++ b/source/blender/windowmanager/intern/wm_window.c
@@ -602,6 +602,7 @@ void WM_window_set_dpi(wmWindow *win)
 	U.dpi = dpi / pixelsize;
 	U.virtual_pixel = (pixelsize == 1) ? VIRTUAL_PIXEL_NATIVE : VIRTUAL_PIXEL_DOUBLE;
 	U.widget_unit = (U.pixelsize * U.dpi * 20 + 36) / 72;
+	U.dpi_fac = ((U.pixelsize * (float)U.dpi) / 72.0f);
 
 	/* update font drawing */
 	BLF_default_dpi(U.pixelsize * U.dpi);