Fixed screenScalingFactor

Signed-off-by: ahcorde <[email protected]>
gazebosim · Feb 2, 2021 · 95a6347 · 95a6347
1 parent 61cc21b
commit 95a6347
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Showing 4 changed files with 81 additions and 6 deletions.
diff --git a/include/ignition/rendering/Utils.hh b/include/ignition/rendering/Utils.hh
@@ -40,6 +40,13 @@ namespace ignition
     IGNITION_RENDERING_VISIBLE
     float screenScalingFactor();
 
+    /// \brief Get the screen scaling factor.
+    /// \param[out] _xScale The X screen scaling factor.
+    /// \param[out] _yScale The Y screen scaling factor.
+    /// \return The screen scaling factor.
+    IGNITION_RENDERING_VISIBLE
+    void screenScalingFactor(float &_xScale, float &_yScale);
+
     /// \brief Transform a bounding box.
     /// \param[in] _box The bounding box.
     /// \param[in] _pose Pose used to transform the bounding box.

diff --git a/ogre/src/OgreCamera.cc b/ogre/src/OgreCamera.cc
@@ -216,10 +216,11 @@ VisualPtr OgreCamera::VisualAt(const ignition::math::Vector2i
     }
   }
 
-  float ratio = screenScalingFactor();
+  float xScale, YScale;
+  screenScalingFactor(xScale, YScale);
   ignition::math::Vector2i mousePos(
-      static_cast<int>(std::rint(ratio * _mousePos.X())),
-      static_cast<int>(std::rint(ratio * _mousePos.Y())));
+      static_cast<int>(std::rint(xScale * _mousePos.X())),
+      static_cast<int>(std::rint(YScale * _mousePos.Y())));
 
   Ogre::Entity *entity = this->selectionBuffer->OnSelectionClick(
       mousePos.X(), mousePos.Y());

diff --git a/ogre2/src/Ogre2Camera.cc b/ogre2/src/Ogre2Camera.cc
@@ -208,10 +208,11 @@ VisualPtr Ogre2Camera::VisualAt(const ignition::math::Vector2i &_mousePos)
     }
   }
 
-  float ratio = screenScalingFactor();
+  float xScale, YScale;
+  screenScalingFactor(xScale, YScale);
   ignition::math::Vector2i mousePos(
-      static_cast<int>(std::rint(ratio * _mousePos.X())),
-      static_cast<int>(std::rint(ratio * _mousePos.Y())));
+      static_cast<int>(std::rint(xScale * _mousePos.X())),
+      static_cast<int>(std::rint(YScale * _mousePos.Y())));
 
   Ogre::Item *ogreItem = this->selectionBuffer->OnSelectionClick(
       mousePos.X(), mousePos.Y());

diff --git a/src/Utils.cc b/src/Utils.cc
@@ -89,6 +89,72 @@ float screenScalingFactor()
   return ratio;
 }
 
+/////////////////////////////////////////////////
+void screenScalingFactor(float &_xScale, float &_yScale)
+{
+  // todo(anyone) set device pixel ratio for high dpi displays on Windows
+#ifdef __linux__
+  auto closeDisplay = [](Display * display)
+  {
+    if (display)
+      XCloseDisplay(display);
+  };
+  auto display =
+    std::unique_ptr<Display, decltype(closeDisplay)>(
+      XOpenDisplay(nullptr), closeDisplay);
+  char *resourceString = XResourceManagerString(display.get());
+
+  if (resourceString)
+  {
+    char *type = nullptr;
+    float dpiDesktop = 0.0;
+
+    // Need to initialize the DB before calling Xrm* functions
+    XrmInitialize();
+
+    XrmValue value;
+    XrmDatabase db = XrmGetStringDatabase(resourceString);
+
+    // Debug:
+    // printf("Entire DB:\n%s\n", resourceString);
+
+    if (XrmGetResource(db, "Xft.dpi", "String", &type, &value) == True)
+    {
+      if (value.addr)
+        dpiDesktop = atof(value.addr);
+    }
+
+    // To get the ratio we need the DPI as reported by the Xrmdatabase,
+    // which takes into account desktop scaling, and the DPI computed by the
+    // actual display resolution.
+    //
+    // dpiRes = N pixels / (M millimeters / (25.4 millimeters / 1 inch))
+    //        = N pixels / (M inch / 25.4)
+    //        = (N * 25.4 pixels) / M inch
+    //
+    // We can use either the width or height in the following line. The zero
+    // values in DisplayHeight and DisplayHeightMM is the screen number. A
+    // value of zero uses the default screen.
+    float xDpiRes = (DisplayWidth(display.get(), 0) * 25.4) /
+      DisplayWidthMM(display.get(), 0);
+    float yDpiRes = (DisplayHeight(display.get(), 0) * 25.4) /
+      DisplayHeightMM(display.get(), 0);
+
+    if (!math::equal(dpiDesktop, 0.0f) && !math::equal(yDpiRes, 0.0f))
+      _yScale = yDpiRes / dpiDesktop;
+    if (_yScale < 1) _yScale = 1;
+
+    if (!math::equal(dpiDesktop, 0.0f) && !math::equal(xDpiRes, 0.0f))
+      _xScale = xDpiRes / dpiDesktop;
+    if (_xScale < 1) _xScale = 1;
+
+    // Debug:
+    // printf("DPI Desktop: %f, DPI XY: [%f, %f], Scale XY: [%f, %f]\n",
+    //   dpiDesktop, xDpiRes, yDpiRes, _xScale, _yScale);
+  }
+#endif
+}
+
 /////////////////////////////////////////////////
 ignition::math::AxisAlignedBox transformAxisAlignedBox(
     const ignition::math::AxisAlignedBox &_bbox,