1 /*
   2  * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 #include "systemScale.h"
  26 #include <jdk_util.h>
  27 #ifndef MDT_EFFECTIVE_DPI
  28 #define MDT_EFFECTIVE_DPI 0
  29 #endif
  30 
  31 void GetScreenDpi(HMONITOR hmon, float *dpiX, float *dpiY)
  32 {
  33     unsigned x = 0;
  34     unsigned y = 0;
  35 
  36     // for debug purposes
  37     static float scale = -2.0f;
  38     if (scale == -2) {
  39         scale = -1;
  40         char *uiScale = getenv("J2D_UISCALE");
  41         if (uiScale != NULL) {
  42             scale = (float)strtod(uiScale, NULL);
  43             if (errno == ERANGE || scale <= 0) {
  44                 scale = -1;
  45             }
  46         }
  47     }
  48 
  49     if (scale > 0) {
  50         *dpiX = *dpiY = scale;
  51         return;
  52     }
  53 
  54     typedef HRESULT(WINAPI GetDpiForMonitorFunc)(HMONITOR, int, UINT*, UINT*);
  55     static HMODULE hLibSHCoreDll = NULL;
  56     static GetDpiForMonitorFunc *lpGetDpiForMonitor = NULL;
  57 
  58     if (hLibSHCoreDll == NULL) {
  59         hLibSHCoreDll = JDK_LoadSystemLibrary("shcore.dll");
  60         if (hLibSHCoreDll != NULL) {
  61             lpGetDpiForMonitor = (GetDpiForMonitorFunc*)GetProcAddress(
  62                 hLibSHCoreDll, "GetDpiForMonitor");
  63         }
  64     }
  65 
  66     if (lpGetDpiForMonitor != NULL) {
  67         HRESULT hResult = lpGetDpiForMonitor(hmon,
  68                                              MDT_EFFECTIVE_DPI, &x, &y);
  69         if (hResult == S_OK) {
  70             *dpiX = static_cast<float>(x);
  71             *dpiY = static_cast<float>(y);
  72         }
  73     } else {
  74         HDC hdc = GetDC(NULL);
  75         if (hdc) {
  76             *dpiX = static_cast<float>(GetDeviceCaps(hdc, LOGPIXELSX));
  77             *dpiY = static_cast<float>(GetDeviceCaps(hdc, LOGPIXELSY));
  78             ReleaseDC(NULL, hdc);
  79         }
  80     }
  81     return;
  82 }
  83 
  84 HMONITOR WINAPI getPrimaryMonitor()
  85 {
  86     const POINT point = { 0, 0 };
  87     return MonitorFromPoint(point, MONITOR_DEFAULTTOPRIMARY);
  88 }