xwayland: Use double for screen size

Use double precision floating point for the screen size to reduce the
rounding issues when using fractional scaling.

Introduce a couple of simple convenient functions that round the
floating point value into an integer and use it in place of directly
accessing the xwl_screen width/height for integer computation.

This is preparation work for the introduction of fractional scaling,
there should be no functional change at this point.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-By: Kenny Levinsen <kl@kl.wtf>
Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1197>

hw/xwayland/xwayland-input.c

@@ -1387,8 +1387,8 @@ xwl_touch_send_event(struct xwl_touch *xwl_touch,
     dx = xwl_touch->window->window->drawable.x;
     dy = xwl_touch->window->window->drawable.y;
 
-    x = (dx + xwl_touch->x) * 0xFFFF / xwl_seat->xwl_screen->width;
+    x = (dx + xwl_touch->x) * 0xFFFF / xwl_screen_get_width(xwl_seat->xwl_screen);
-    y = (dy + xwl_touch->y) * 0xFFFF / xwl_seat->xwl_screen->height;
+    y = (dy + xwl_touch->y) * 0xFFFF / xwl_screen_get_height(xwl_seat->xwl_screen);
 
     valuator_mask_zero(&mask);
     valuator_mask_set_double(&mask, 0, x);

hw/xwayland/xwayland-output.c

@@ -25,6 +25,8 @@
 
 #include <xwayland-config.h>
 
+#include <math.h>
+
 #include <X11/Xatom.h>
 #include "randrstr_priv.h"
 
@@ -186,8 +188,11 @@ update_backing_pixmaps(struct xwl_screen *xwl_screen, int width, int height)
 static void
 update_screen_size(struct xwl_screen *xwl_screen, int width, int height)
 {
-    xwl_screen->width = width;
+    if (xwl_screen_get_width(xwl_screen) != width)
-    xwl_screen->height = height;
+        xwl_screen->width = width;
+
+    if (xwl_screen_get_height(xwl_screen) != height)
+        xwl_screen->height = height;
 
     if (xwl_screen->root_clip_mode == ROOT_CLIP_FULL)
         SetRootClip(xwl_screen->screen, ROOT_CLIP_NONE);
@@ -486,8 +491,8 @@ xwl_output_get_emulated_root_size(struct xwl_output *xwl_output,
     emulated_mode = xwl_output_get_emulated_mode_for_client(xwl_output, client);
     /* If not an emulated mode, just return the actual screen size */
     if (!emulated_mode) {
-        *width = xwl_screen->width;
+        *width = xwl_screen_get_width(xwl_screen);
-        *height = xwl_screen->height;
+        *height = xwl_screen_get_height(xwl_screen);
         return;
     }
 
@@ -1247,10 +1252,12 @@ xwl_screen_init_randr_fixed(struct xwl_screen *xwl_screen)
     RROutputSetCrtcs(xwl_output->randr_output, &xwl_output->randr_crtc, 1);
 
     xwl_randr_add_modes_fixed(xwl_output,
-                              xwl_screen->width, xwl_screen->height);
+                              xwl_screen_get_width(xwl_screen),
+                              xwl_screen_get_height(xwl_screen));
     /* Current mode */
     mode = xwl_output_find_mode(xwl_output,
-                                xwl_screen->width, xwl_screen->height);
+                                xwl_screen_get_width(xwl_screen),
+                                xwl_screen_get_height(xwl_screen));
     RRCrtcNotify(xwl_output->randr_crtc, mode, 0, 0, RR_Rotate_0,
                  NULL, 1, &xwl_output->randr_output);
 

hw/xwayland/xwayland-screen.c

@@ -25,6 +25,7 @@
 
 #include <xwayland-config.h>
 
+#include <math.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <errno.h>
@@ -145,6 +146,18 @@ xwl_screen_get_fixed_or_first_output(struct xwl_screen *xwl_screen)
     return xwl_screen_get_first_output(xwl_screen);
 }
 
+int
+xwl_screen_get_width(struct xwl_screen *xwl_screen)
+{
+    return round(xwl_screen->width);
+}
+
+int
+xwl_screen_get_height(struct xwl_screen *xwl_screen)
+{
+    return round(xwl_screen->height);
+}
+
 static void
 xwl_property_callback(CallbackListPtr *pcbl, void *closure,
                       void *calldata)
@@ -966,7 +979,8 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
     miSetPixmapDepths();
 
     ret = fbScreenInit(pScreen, NULL,
-                       xwl_screen->width, xwl_screen->height,
+                       xwl_screen_get_width(xwl_screen),
+                       xwl_screen_get_height(xwl_screen),
                        monitorResolution, monitorResolution, 0,
                        BitsPerPixel(xwl_screen->depth));
     if (!ret)

hw/xwayland/xwayland-screen.h

@@ -45,8 +45,8 @@
 #endif
 
 struct xwl_screen {
-    int width;
+    double width;
-    int height;
+    double height;
     int depth;
     int output_name_serial;
     ScreenPtr screen;
@@ -157,6 +157,9 @@ Bool xwl_screen_has_resolution_change_emulation(struct xwl_screen *xwl_screen);
 void xwl_screen_check_resolution_change_emulation(struct xwl_screen *xwl_screen);
 struct xwl_output *xwl_screen_get_first_output(struct xwl_screen *xwl_screen);
 struct xwl_output *xwl_screen_get_fixed_or_first_output(struct xwl_screen *xwl_screen);
+int xwl_screen_get_width(struct xwl_screen *xwl_screen);
+int xwl_screen_get_height(struct xwl_screen *xwl_screen);
+
 Bool xwl_close_screen(ScreenPtr screen);
 Bool xwl_screen_init(ScreenPtr pScreen, int argc, char **argv);
 void xwl_sync_events (struct xwl_screen *xwl_screen);

hw/xwayland/xwayland-window.c

@@ -346,8 +346,8 @@ xwl_window_should_enable_viewport_fullscreen(struct xwl_window *xwl_window,
 
     *xwl_output_ret = xwl_output;
     emulated_mode_ret->server_output_id = 0;
-    emulated_mode_ret->width = xwl_screen->width;
+    emulated_mode_ret->width = xwl_screen_get_width(xwl_screen);
-    emulated_mode_ret->height = xwl_screen->height;
+    emulated_mode_ret->height = xwl_screen_get_height(xwl_screen);
     emulated_mode_ret->from_vidmode = FALSE;
 
     return TRUE;
@@ -411,8 +411,8 @@ xwl_window_should_enable_viewport(struct xwl_window *xwl_window,
     if (xwl_output && xwl_window->window->overrideRedirect &&
         emulated_mode && emulated_mode->from_vidmode &&
         drawable->x == 0 && drawable->y == 0 &&
-        drawable->width  == xwl_screen->width &&
+        drawable->width  == xwl_screen_get_width(xwl_screen) &&
-        drawable->height == xwl_screen->height) {
+        drawable->height == xwl_screen_get_height(xwl_screen)) {
 
         memcpy(emulated_mode_ret, emulated_mode, sizeof(struct xwl_emulated_mode));
         *xwl_output_ret = xwl_output;
@@ -637,7 +637,7 @@ xwl_window_rootful_set_app_id(struct xwl_window *xwl_window)
 }
 
 static void
-xwl_window_maybe_resize(struct xwl_window *xwl_window, int width, int height)
+xwl_window_maybe_resize(struct xwl_window *xwl_window, double width, double height)
 {
     struct xwl_screen *xwl_screen = xwl_window->xwl_screen;
     struct xwl_output *xwl_output;
@@ -650,11 +650,14 @@ xwl_window_maybe_resize(struct xwl_window *xwl_window, int width, int height)
     if (width == xwl_screen->width && height == xwl_screen->height)
         return;
 
+    xwl_screen->width = width;
+    xwl_screen->height = height;
+
     xwl_output = xwl_screen_get_fixed_or_first_output(xwl_screen);
-    if (!xwl_randr_add_modes_fixed(xwl_output, width, height))
+    if (!xwl_randr_add_modes_fixed(xwl_output, round(width), round(height)))
         return;
 
-    mode = xwl_output_find_mode(xwl_output, width, height);
+    mode = xwl_output_find_mode(xwl_output,  round(width), round(height));
     xwl_output_set_mode_fixed(xwl_output, mode);
 
     xwl_window_attach_buffer(xwl_window);
@@ -692,15 +695,17 @@ handle_libdecor_configure(struct libdecor_frame *frame,
     struct xwl_window *xwl_window = data;
     struct xwl_screen *xwl_screen = xwl_window->xwl_screen;
     int width, height;
+    double new_width, new_height;
 
-    if (!libdecor_configuration_get_content_size(configuration, frame, &width, &height)) {
+    if (libdecor_configuration_get_content_size(configuration, frame, &width, &height)) {
-        width = xwl_screen->width;
+        new_width = (double) width;
-        height = xwl_screen->height;
+        new_height = (double) height;
     }
 
-    xwl_window_maybe_resize(xwl_window, width, height);
+    xwl_window_maybe_resize(xwl_window, new_width, new_height);
     xwl_window_update_libdecor_size(xwl_window, configuration,
-                                    xwl_screen->width, xwl_screen->height);
+                                     xwl_screen_get_width(xwl_screen),
+                                     xwl_screen_get_height(xwl_screen));
     wl_surface_commit(xwl_window->surface);
 }
 
@@ -1023,7 +1028,12 @@ xwl_realize_window(WindowPtr window)
         }
 
         if (!window->parent) {
-            BoxRec box = { 0, 0, xwl_screen->width, xwl_screen->height };
+            BoxRec box = {
+                0,
+                0,
+                xwl_screen_get_width(xwl_screen),
+                xwl_screen_get_height(xwl_screen)
+            };
 
             RegionReset(&window->winSize, &box);
             RegionNull(&window->clipList);