From cdc67e80ac78d08aee04bbc55ece650579beba6c Mon Sep 17 00:00:00 2001
From: Jonas Kümmerlin <jonas@kuemmerlin.eu>
Date: Fri, 19 Jun 2020 16:48:18 +0200
Subject: add functions for centering a toplevel window on the monitor

---
 alf/alftoplevel.cpp | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

(limited to 'alf/alftoplevel.cpp')

diff --git a/alf/alftoplevel.cpp b/alf/alftoplevel.cpp
index 11e8599..0747ea2 100644
--- a/alf/alftoplevel.cpp
+++ b/alf/alftoplevel.cpp
@@ -594,6 +594,69 @@ ALF_Toplevel_SetDefaultFont(HWND toplevel)
     SendMessage(toplevel, ALF_WM_TPLVL_SETDEFFONT, 0, 0);
 }
 
+void
+ALF_Toplevel_CenterOnMonitor(HWND toplevel, HMONITOR monitor)
+{
+    MONITORINFO mi;
+    ZeroMemory(&mi, sizeof(mi));
+    mi.cbSize = sizeof(mi);
+
+    if (ALF_Compat_GetMonitorInfoA(monitor, &mi)) {
+        MINMAXINFO i;
+        ZeroMemory(&i, sizeof(i));
+        SendMessage(toplevel, WM_GETMINMAXINFO, 0, (LPARAM)&i);
+
+        RECT rcWindow = {0,0,0,0};
+        GetWindowRect(toplevel, &rcWindow);
+
+        int width = rcWindow.right - rcWindow.left;
+        if (width < i.ptMinTrackSize.x)
+            width = i.ptMinTrackSize.x;
+
+        int height = rcWindow.bottom - rcWindow.top;
+        if (height < i.ptMinTrackSize.y)
+            height = i.ptMinTrackSize.y;
+
+        RECT rcTarget;
+        rcTarget.left = (mi.rcWork.left + mi.rcWork.right - width) / 2;
+        rcTarget.top  = (mi.rcWork.top + mi.rcWork.bottom - height) / 2;
+        rcTarget.right = rcTarget.left + width;
+        rcTarget.bottom = rcTarget.top + height;
+
+        OffsetRect(&rcTarget, mi.rcMonitor.left - mi.rcWork.left, mi.rcMonitor.top - mi.rcWork.top);
+
+        WINDOWPLACEMENT wp;
+        ZeroMemory(&wp, sizeof(wp));
+        wp.length = sizeof(wp);
+
+        GetWindowPlacement(toplevel, &wp);
+
+        wp.rcNormalPosition = rcTarget;
+
+        SetWindowPlacement(toplevel, &wp);
+    }
+}
+
+void
+ALF_Toplevel_CenterOnCurrentMonitor(HWND toplevel)
+{
+    ALF_Toplevel_CenterOnMonitor(toplevel, ALF_Compat_MonitorFromWindow(toplevel, MONITOR_DEFAULTTONEAREST));
+}
+
+void
+ALF_Toplevel_CenterOnOwnerMonitor(HWND toplevel)
+{
+    HWND hwndOwner = GetParent(toplevel);
+    ALF_Toplevel_CenterOnMonitor(toplevel, ALF_Compat_MonitorFromWindow(hwndOwner, MONITOR_DEFAULTTONEAREST));
+}
+
+void
+ALF_Toplevel_CenterOnPrimaryMonitor(HWND toplevel)
+{
+    POINT ptZero = { 0, 0 };
+    ALF_Toplevel_CenterOnMonitor(toplevel, ALF_Compat_MonitorFromPoint(ptZero, MONITOR_DEFAULTTOPRIMARY));
+}
+
 ALFApplication *
 ALF_CreateApplication(void)
 {
-- 
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