[c-host] dxgi: use low level mouse input by default

This is known to prevent cursor updates on the secure desktop
(UAC) but DXGI DD does not provide us with the real mouse
coordinates when applications have 'captured' the cursor.

c-host/platform/Windows/capture/DXGI/src/dxgi.c

@@ -25,6 +25,8 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 #include "common/locking.h"
 #include "common/event.h"
 
+#include "windows/mousehook.h"
+
 #include <assert.h>
 #include <dxgi.h>
 #include <d3d11.h>
@@ -82,6 +84,9 @@ struct iface
   unsigned int  stride;
   CaptureFormat format;
 
+  LG_Lock pointerLock;
+  bool decouplePointer;
+  int  hotspotX    , hotspotY;
   int  lastPointerX, lastPointerY;
   bool lastPointerVisible;
 };
@@ -96,6 +101,28 @@ static CaptureResult dxgi_releaseFrame();
 
 // implementation
 
+static void on_mouseMove(int x, int y)
+{
+  LG_LOCK(this->pointerLock);
+
+  x -= this->hotspotX;
+  y -= this->hotspotY;
+
+  this->lastPointerX = x;
+  this->lastPointerY = y;
+
+  CapturePointer pointer =
+  {
+    .positionUpdate = true,
+    .visible        = this->lastPointerVisible,
+    .x              = x,
+    .y              = y
+  };
+  this->postPointerBufferFn(pointer);
+
+  LG_UNLOCK(this->pointerLock);
+}
+
 static const char * dxgi_getName()
 {
   return "DXGI";
@@ -133,6 +160,14 @@ static void dxgi_initOptions()
       .type           = OPTION_TYPE_BOOL,
       .value.x_bool   = false
     },
+    {
+      .module         = "dxgi",
+      .name           = "decouplePointer",
+      .description    = "Use a low level hook to obtain cursor position information",
+      .type           = OPTION_TYPE_BOOL,
+      .value.x_bool   = true
+    },
+
     {0}
   };
 
@@ -161,10 +196,18 @@ static bool dxgi_create(CaptureGetPointerBuffer getPointerBufferFn, CapturePostP
   if (this->maxTextures <= 0)
     this->maxTextures = 1;
 
-  this->useAcquireLock      = option_get_bool("dxgi", "useAcquireLock");
+  this->useAcquireLock  = option_get_bool("dxgi", "useAcquireLock" );
+  this->decouplePointer = option_get_bool("dxgi", "decouplePointer");
+
   this->texture             = calloc(sizeof(struct Texture), this->maxTextures);
   this->getPointerBufferFn  = getPointerBufferFn;
   this->postPointerBufferFn = postPointerBufferFn;
+
+  LG_LOCK_INIT(this->pointerLock);
+
+  if (this->decouplePointer)
+    mouseHook_install(on_mouseMove);
+
   return true;
 }
 
@@ -529,6 +572,8 @@ static bool dxgi_deinit()
 {
   assert(this);
 
+  mouseHook_remove();
+
   for(int i = 0; i < this->maxTextures; ++i)
   {
     this->texture[i].state = TEXTURE_STATE_UNUSED;
@@ -712,22 +757,20 @@ static CaptureResult dxgi_capture()
       frameInfo.PointerPosition.Visible    != this->lastPointerVisible
       )
     {
+      LG_LOCK(this->pointerLock);
+
       /* the pointer position is invalid if the pointer is not visible */
-      if (frameInfo.PointerPosition.Visible)
+      if (!this->decouplePointer && frameInfo.PointerPosition.Visible)
       {
         pointer.positionUpdate = true;
-        pointer.x =
-          this->lastPointerX =
-          frameInfo.PointerPosition.Position.x;
-        pointer.y =
-          this->lastPointerY =
-          frameInfo.PointerPosition.Position.y;
+        this->lastPointerX = frameInfo.PointerPosition.Position.x;
+        this->lastPointerY = frameInfo.PointerPosition.Position.y;
       }
 
-      pointer.visible =
-        this->lastPointerVisible =
-        frameInfo.PointerPosition.Visible;
+      this->lastPointerVisible = frameInfo.PointerPosition.Visible;
       postPointer = true;
+
+      LG_UNLOCK(this->pointerLock);
     }
   }
 
@@ -758,6 +801,12 @@ static CaptureResult dxgi_capture()
           return CAPTURE_RESULT_ERROR;
       }
 
+      // needed in decouple mode
+      LG_LOCK(this->pointerLock);
+      this->hotspotX = shapeInfo.HotSpot.x;
+      this->hotspotY = shapeInfo.HotSpot.y;
+      LG_UNLOCK(this->pointerLock);
+
       pointer.shapeUpdate = true;
       pointer.width       = shapeInfo.Width;
       pointer.height      = shapeInfo.Height;
@@ -768,7 +817,12 @@ static CaptureResult dxgi_capture()
 
   // post back the pointer information
   if (postPointer)
+  {
+    LG_LOCK(this->pointerLock);
+    pointer.visible = this->lastPointerVisible;
     this->postPointerBufferFn(pointer);
+    LG_UNLOCK(this->pointerLock);
+  }
 
   return CAPTURE_RESULT_OK;
 }