Automatic DPI for all platforms, per monitor DPI for Windows.

For Windows 8.1 and X11 (Linux, BSD) now use the DPI specified by the operating
system, which previously only worked on macOS. For Windows this is handled per
monitor, for X11 this is based on Xft.dpi or xrandr --dpi. This should result
in appropriate font and button sizes by default in most cases.

The UI has been simplified to a single UI Scale factor relative to the automatic
DPI, instead of two DPI and Virtual Pixel Size settings. There is forward and
backwards compatibility for existing user preferences.

Reviewed By: brecht, LazyDodo

Differential Revision: https://developer.blender.org/D2539

1 files changed, 52 insertions, 19 deletions

diff --git a/source/blender/windowmanager/intern/wm_window.c b/source/blender/windowmanager/intern/wm_window.c
index 2d43c47679d..40baab8809c 100644
--- a/source/blender/windowmanager/intern/wm_window.c
+++ b/source/blender/windowmanager/intern/wm_window.c
@@ -77,6 +77,7 @@
 #include "GPU_extensions.h"
 #include "GPU_init_exit.h"
 #include "GPU_glew.h"
+#include "BLF_api.h"
 
 /* for assert */
 #ifndef NDEBUG
@@ -374,14 +375,39 @@ void wm_window_title(wmWindowManager *wm, wmWindow *win)
 	}
 }
 
-static float wm_window_get_virtual_pixelsize(void)
+static void wm_window_set_dpi(wmWindow *win)
 {
-	return ((U.virtual_pixel == VIRTUAL_PIXEL_NATIVE) ? 1.0f : 2.0f);
-}
+	int auto_dpi = GHOST_GetDPIHint(win->ghostwin);
 
-float wm_window_pixelsize(wmWindow *win)
-{
-	return (GHOST_GetNativePixelSize(win->ghostwin) * wm_window_get_virtual_pixelsize());
+	/* Lazily init UI scale size, preserving backwards compatibility by
+	 * computing UI scale from ratio of previous DPI and auto DPI */
+	if (U.ui_scale == 0) {
+		int virtual_pixel = (U.virtual_pixel == VIRTUAL_PIXEL_NATIVE) ? 1 : 2;
+
+		if (U.dpi == 0) {
+			U.ui_scale = virtual_pixel;
+		}
+		else {
+			U.ui_scale = (virtual_pixel * U.dpi * 96.0f) / (auto_dpi * 72.0f);
+		}
+
+		CLAMP(U.ui_scale, 0.25f, 4.0f);
+	}
+
+	/* Blender's UI drawing assumes DPI 72 as a good default following macOS
+	 * while Windows and Linux use DPI 96. GHOST assumes a default 96 so we
+	 * remap the DPI to Blender's convention. */
+	int dpi = auto_dpi * U.ui_scale * (72.0/96.0f);
+
+	/* Automatically set larger pixel size for high DPI. */
+	int pixelsize = MAX2(1, dpi / 54);
+
+	/* Set user preferences globals for drawing, and for forward compatibility. */
+	U.pixelsize = GHOST_GetNativePixelSize(win->ghostwin) * pixelsize;
+	U.dpi = dpi / pixelsize;
+	U.virtual_pixel = (pixelsize == 1) ? VIRTUAL_PIXEL_NATIVE : VIRTUAL_PIXEL_DOUBLE;
+
+	BKE_blender_userdef_refresh();
 }
 
 /* belongs to below */
@@ -456,10 +482,8 @@ static void wm_window_ghostwindow_add(wmWindowManager *wm, const char *title, wm
 			glClear(GL_COLOR_BUFFER_BIT);
 		}
 		
-		/* displays with larger native pixels, like Macbook. Used to scale dpi with */
 		/* needed here, because it's used before it reads userdef */
-		U.pixelsize = wm_window_pixelsize(win);
-		BKE_blender_userdef_refresh();
+		wm_window_set_dpi(win);
 		
 		wm_window_swap_buffers(win);
 		
@@ -626,7 +650,6 @@ wmWindow *WM_window_open_temp(bContext *C, const rcti *rect_init, int type)
 	Scene *scene = CTX_data_scene(C);
 	const char *title;
 	rcti rect = *rect_init;
-	const short px_virtual = (short)wm_window_get_virtual_pixelsize();
 
 	/* changes rect to fit within desktop */
 	wm_window_check_position(&rect);
@@ -644,9 +667,8 @@ wmWindow *WM_window_open_temp(bContext *C, const rcti *rect_init, int type)
 		win->posy = rect.ymin;
 	}
 
-	/* multiply with virtual pixelsize, ghost handles native one (e.g. for retina) */
-	win->sizex = BLI_rcti_size_x(&rect) * px_virtual;
-	win->sizey = BLI_rcti_size_y(&rect) * px_virtual;
+	win->sizex = BLI_rcti_size_x(&rect);
+	win->sizey = BLI_rcti_size_y(&rect);
 
 	if (win->ghostwin) {
 		wm_window_set_size(win, win->sizex, win->sizey);
@@ -835,8 +857,7 @@ void wm_window_make_drawable(wmWindowManager *wm, wmWindow *win)
 		GHOST_ActivateWindowDrawingContext(win->ghostwin);
 		
 		/* this can change per window */
-		U.pixelsize = wm_window_pixelsize(win);
-		BKE_blender_userdef_refresh();
+		wm_window_set_dpi(win);
 	}
 }
 
@@ -1035,6 +1056,8 @@ static int ghost_event_proc(GHOST_EventHandle evt, GHOST_TUserDataPtr C_void_ptr
 				if (type == GHOST_kEventWindowSize) {
 					WM_jobs_stop(wm, win->screen, NULL);
 				}
+
+				wm_window_set_dpi(win);
 				
 				/* win32: gives undefined window size when minimized */
 				if (state != GHOST_kWindowStateMinimized) {
@@ -1118,7 +1141,19 @@ static int ghost_event_proc(GHOST_EventHandle evt, GHOST_TUserDataPtr C_void_ptr
 				}
 				break;
 			}
-				
+
+			case GHOST_kEventWindowDPIHintChanged:
+			{
+				wm_window_set_dpi(win);
+				/* font's are stored at each DPI level, without this we can easy load 100's of fonts */
+				BLF_cache_clear();
+
+				BKE_blender_userdef_refresh();
+				WM_main_add_notifier(NC_WINDOW, NULL);      /* full redraw */
+				WM_main_add_notifier(NC_SCREEN | NA_EDITED, NULL);    /* refresh region sizes */
+				break;
+			}
+
 			case GHOST_kEventOpenMainFile:
 			{
 				PointerRNA props_ptr;
@@ -1199,11 +1234,9 @@ static int ghost_event_proc(GHOST_EventHandle evt, GHOST_TUserDataPtr C_void_ptr
 			{
 				// only update if the actual pixel size changes
 				float prev_pixelsize = U.pixelsize;
-				U.pixelsize = wm_window_pixelsize(win);
+				wm_window_set_dpi(win);
 
 				if (U.pixelsize != prev_pixelsize) {
-					BKE_blender_userdef_refresh();
-
 					// close all popups since they are positioned with the pixel
 					// size baked in and it's difficult to correct them
 					wmWindow *oldWindow = CTX_wm_window(C);