Point picking broken on macos

[themightyoarfish]

Based on #153, a minmal example to pick points on a Cube creates nonsensical 3d points.

In the attached images, cursor shows click location, red ball is the selected point.

Often, nothing at all is selected. What could this be caused by? Could it be related to retina display scaling factor somehow?

Related: koide3/direct_visual_lidar_calibration#154

[themightyoarfish]

it's notable that this does not seem to be random, rather there is an offset between the cursor and the picked point.

CleanShot.2025-07-27.at.16.27.48.mp4

[themightyoarfish]

Ok i am making some progress here. The default viewer instance size is 1920x1080, this is larger than my display size, depending on the scaling factor, i have choosen the "resolution" (actually the scaling, the resolution is always the same i think) to be 1496x967. If i get a Lighviewer instance with a smaller size that fits inside this, then the picking behaves like expected. So somehow theres a bug in the viewer that will cause the picking to fail when the size is larger than the screen, even though what gets displayed is properly resized to the screen dimensions.

[themightyoarfish]

But then when I resized the window in any way, it breaks again.

[themightyoarfish]

It also looks like Application::resize() is never called, thus glfw is somehow not getting informed of the new window size?

[themightyoarfish]

Another maybe related observation: the size of the frame buffer changes a lot with small changes in window size. If i start out with a window of 926 x 600 and then enlarge it by the minimum increment with the mouse, suddenly the frame buffer reports the size as 1848 x 1188 for instance.

[themightyoarfish]

It seems like this diff makes it work, but i am not sure if this is the only place where display scale needs to be considered

diff --git a/src/guik/imgui_application.cpp b/src/guik/imgui_application.cpp
index fc003da..cd4986f 100644
--- a/src/guik/imgui_application.cpp
+++ b/src/guik/imgui_application.cpp
@@ -37,7 +37,12 @@ Application ::~Application() {
 // dirty implementation
 std::unordered_map<GLFWwindow*, Application*> appmap;
 void fb_size_callback(GLFWwindow* window, int width, int height) {
-  appmap[window]->framebuffer_size_callback(Eigen::Vector2i(width, height));
+  GLFWmonitor* screen = glfwGetWindowMonitor(window);
+  float xscale, yscale;
+  glfwGetMonitorContentScale(screen, &xscale, &yscale);
+  appmap[window]->framebuffer_size_callback(Eigen::Vector2i(width/xscale, height/yscale));
+
+
 }

[themightyoarfish]

Unfortunately does not fully solve koide3/direct_visual_lidar_calibration#154

[themightyoarfish]

It seems that ImGUI simply does not support high dpi, kinda strange that this needs to be found out via googling a bunch, i guess no one uses it on macbooks? Apparently there are some platform differences to how screen sizes are reported, so this either needs to be worked around in the application, or in ImGUI itself:

ocornut/imgui#3757 (comment)

[themightyoarfish]

First potential fix on #153