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Fix setting physical output size in Xephyr
Needed for DPI detection in sys-gui QubesOS/qubes-issues#10840
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‎0001-Xephyr-fix-setting-physical-output-size.patch‎

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From 6bd9aec85f329def9ed97956d13f990bb8fbd7eb Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
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<marmarek@invisiblethingslab.com>
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Date: Wed, 17 Jun 2026 20:22:20 +0200
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Subject: [PATCH] Xephyr: fix setting physical output size
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Providing physical size via RRRegisterSize() is not enough - physical
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size is a property of the output, not resolution and needs to be set
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separately. Furhermore, get the physical output size using RandR if
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-output is used, to match specific output, not the whole screen.
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With this, `Xephyr -output OUTPUT_NAME` properly copies not only
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resolution but also physical size of the named output.
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Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
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---
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hw/kdrive/ephyr/ephyr.c | 8 ++++++++
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hw/kdrive/ephyr/ephyr.h | 1 +
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hw/kdrive/ephyr/hostx.c | 15 +++++++++++----
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hw/kdrive/ephyr/hostx.h | 3 ++-
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4 files changed, 22 insertions(+), 5 deletions(-)
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diff --git a/hw/kdrive/ephyr/ephyr.c b/hw/kdrive/ephyr/ephyr.c
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index 069270219..e62c46912 100644
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--- a/hw/kdrive/ephyr/ephyr.c
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+++ b/hw/kdrive/ephyr/ephyr.c
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@@ -453,6 +453,14 @@ ephyrRandRGetInfo(ScreenPtr pScreen, Rotation * rotations)
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screen->width,
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screen->height, screen->width_mm, screen->height_mm);
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+ if (hostx_want_fullscreen()) {
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+ RROutputPtr pOutput = RRFirstOutput(pScreen);
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+ if (pOutput)
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+ RROutputSetPhysicalSize(pOutput,
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+ scrpriv->win_width_mm,
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+ scrpriv->win_height_mm);
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+ }
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+
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randr = KdSubRotation(scrpriv->randr, screen->randr);
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RRSetCurrentConfig(pScreen, randr, 0, pSize);
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diff --git a/hw/kdrive/ephyr/ephyr.h b/hw/kdrive/ephyr/ephyr.h
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index 8833de8a9..67e24b3e8 100644
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--- a/hw/kdrive/ephyr/ephyr.h
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+++ b/hw/kdrive/ephyr/ephyr.h
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@@ -76,6 +76,7 @@ typedef struct _ephyrScrPriv {
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Bool win_explicit_position;
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int win_x, win_y;
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int win_width, win_height;
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+ int win_width_mm, win_height_mm;
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int server_depth;
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const char *output; /* Set via -output option */
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unsigned char *fb_data; /* only used when host bpp != server bpp */
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diff --git a/hw/kdrive/ephyr/hostx.c b/hw/kdrive/ephyr/hostx.c
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index b7ac56d50..78e957176 100644
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--- a/hw/kdrive/ephyr/hostx.c
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+++ b/hw/kdrive/ephyr/hostx.c
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@@ -238,7 +238,8 @@ hostx_want_preexisting_window(KdScreenInfo *screen)
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void
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hostx_get_output_geometry(const char *output,
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int *x, int *y,
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- int *width, int *height)
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+ int *width, int *height,
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+ int *width_mm, int *height_mm)
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{
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int i, name_len = 0, output_found = FALSE;
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char *name = NULL;
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@@ -331,6 +332,8 @@ hostx_get_output_geometry(const char *output,
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*y = crtc_info_r->y;
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*width = crtc_info_r->width;
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*height = crtc_info_r->height;
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+ *width_mm = output_info_r->mm_width;
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+ *height_mm = output_info_r->mm_height;
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free(crtc_info_r);
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}
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@@ -628,8 +631,10 @@ hostx_init(void)
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"(ctrl+shift grabs mouse and keyboard)");
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if (HostX.use_fullscreen) {
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- scrpriv->win_width = xscreen->width_in_pixels;
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- scrpriv->win_height = xscreen->height_in_pixels;
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+ scrpriv->win_width = xscreen->width_in_pixels;
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+ scrpriv->win_height = xscreen->height_in_pixels;
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+ scrpriv->win_width_mm = xscreen->width_in_millimeters;
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+ scrpriv->win_height_mm = xscreen->height_in_millimeters;
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hostx_set_fullscreen_hint();
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}
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@@ -638,7 +643,9 @@ hostx_init(void)
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&scrpriv->win_x,
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&scrpriv->win_y,
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&scrpriv->win_width,
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- &scrpriv->win_height);
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+ &scrpriv->win_height,
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+ &scrpriv->win_width_mm,
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+ &scrpriv->win_height_mm);
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HostX.use_fullscreen = TRUE;
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hostx_set_fullscreen_hint();
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diff --git a/hw/kdrive/ephyr/hostx.h b/hw/kdrive/ephyr/hostx.h
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index 8b3caf245..00891a07a 100644
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--- a/hw/kdrive/ephyr/hostx.h
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+++ b/hw/kdrive/ephyr/hostx.h
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@@ -84,7 +84,8 @@ xcb_cursor_t
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void
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hostx_get_output_geometry(const char *output,
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int *x, int *y,
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- int *width, int *height);
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+ int *width, int *height,
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+ int *width_mm, int *height_mm);
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void
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hostx_use_fullscreen(void);
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--
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2.54.0
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‎xorg-x11-server.spec.in‎

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@@ -45,6 +45,8 @@ Patch3: 0001-Fedora-hack-Make-the-suid-root-wrapper-always-start-.patch
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Patch6: 0001-xfree86-fix-enumerating-resolutions-on-NovaCustom-V5.patch
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# backport necessary for the above patch to be effective
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Patch7: 0002-hw-xfree86-re-calculate-the-clock-and-refresh-rate.patch
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# needed for proper DPI detection in sys-gui
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Patch8: 0001-Xephyr-fix-setting-physical-output-size.patch
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BuildRequires: bison
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BuildRequires: flex

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