get display DPI info to scale mouse movement

common/include/common/KVMFR.h

@@ -57,7 +57,7 @@ typedef enum CursorType
 CursorType;
 
 #define KVMFR_MAGIC   "KVMFR---"
-#define KVMFR_VERSION 5
+#define KVMFR_VERSION 6
 
 typedef struct KVMFR
 {
@@ -80,12 +80,13 @@ KVMFRCursor;
 
 typedef struct KVMFRFrame
 {
-  uint32_t  formatVer;   // the frame format version number
-  FrameType type;        // the frame data type
-  uint32_t  width;       // the width
-  uint32_t  height;      // the height
-  uint32_t  stride;      // the row stride (zero if compressed data)
-  uint32_t  pitch;       // the row pitch  (stride in bytes or the compressed frame size)
-  uint32_t  offset;      // offset from the start of this header to the FrameBuffer header
+  uint32_t  formatVer;         // the frame format version number
+  FrameType type;              // the frame data type
+  uint32_t  width;             // the width
+  uint32_t  height;            // the height
+  uint32_t  stride;            // the row stride (zero if compressed data)
+  uint32_t  pitch;             // the row pitch  (stride in bytes or the compressed frame size)
+  uint32_t  offset;            // offset from the start of this header to the FrameBuffer header
+  uint32_t  mouseScalePercent; // movement scale factor of the mouse (relates to DPI of display, 100 = no scale)
 }
 KVMFRFrame;

common/include/common/dpi.h

@@ -0,0 +1,25 @@
+/*
+Looking Glass - KVM FrameRelay (KVMFR) Client
+Copyright (C) 2017-2020 Geoffrey McRae <geoff@hostfission.com>
+https://looking-glass.hostfission.com
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 2 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#include <windows.h>
+
+// At 100% scaling, Windows reports 96 DPI.
+#define DPI_100_PERCENT 96
+
+UINT monitor_dpi(HMONITOR hMonitor);

common/src/platform/windows/CMakeLists.txt

@@ -7,6 +7,7 @@ include_directories(
 
 add_library(lg_common_platform_code STATIC
     crash.c
+    dpi.c
     sysinfo.c
     thread.c
     event.c

common/src/platform/windows/dpi.c

@@ -0,0 +1,37 @@
+#include "common/dpi.h"
+#include "common/windebug.h"
+
+typedef enum MONITOR_DPI_TYPE {
+  MDT_EFFECTIVE_DPI,
+  MDT_ANGULAR_DPI,
+  MDT_RAW_DPI,
+  MDT_DEFAULT
+} MONITOR_DPI_TYPE;
+typedef HRESULT (WINAPI *GetDpiForMonitor_t)(HMONITOR hmonitor, MONITOR_DPI_TYPE dpiType, UINT * dpiX, UINT * dpiY);
+
+UINT monitor_dpi(HMONITOR hMonitor)
+{
+  HMODULE shcore = LoadLibraryA("shcore.dll");
+  if (!shcore)
+  {
+    DEBUG_ERROR("Could not load shcore.dll");
+    return DPI_100_PERCENT;
+  }
+
+  GetDpiForMonitor_t GetDpiForMonitor = (GetDpiForMonitor_t) GetProcAddress(shcore, "GetDpiForMonitor");
+  if (!GetDpiForMonitor)
+  {
+    DEBUG_ERROR("Could not find GetDpiForMonitor");
+    return DPI_100_PERCENT;
+  }
+
+  UINT dpiX, dpiY;
+  HRESULT status = GetDpiForMonitor(hMonitor, MDT_EFFECTIVE_DPI, &dpiX, &dpiY);
+  if (FAILED(status))
+  {
+    DEBUG_WINERROR("GetDpiForMonitor failed", status);
+    return DPI_100_PERCENT;
+  }
+
+  return dpiX;
+}