how do I make wxWidgets (using golang) repaint window on MacOS? - go

Question

Here's some sample code that puts a Gauge on the screen and make the progress bar increase 1 value every second. On MacOS I don't see the progress bar update unless I drag the window around or resize it manually with the mouse. Any idea how to force the whole thing to repaint? I'm calling f.Refresh() and f.Update()
package main
import "github.com/dontpanic92/wxGo/wx"
import "time"
var g wx.Gauge
type MyFrame struct {
wx.Frame
}
func (f *MyFrame) startUpload() {
for {
time.Sleep(time.Second)
g.SetValue(g.GetValue() + 1)
f.Refresh()
f.Update()
}
}
func NewMyFrame() MyFrame {
f := MyFrame{}
f.Frame = wx.NewFrame(wx.NullWindow, -1, "Test Thread")
mainSizer := wx.NewBoxSizer(wx.HORIZONTAL)
g = wx.NewGauge(f, wx.ID_ANY, 100, wx.DefaultPosition, wx.NewSize(600, 40), 0)
f.SetSizer(mainSizer)
mainSizer.Add(g, 100, wx.ALL|wx.EXPAND, 50)
f.Layout()
go f.startUpload()
return f
}
func main() {
wx1 := wx.NewApp()
f := NewMyFrame()
f.Show()
wx1.MainLoop()
return
}
Update: I've been reading http://docs.wxwidgets.org/trunk/overview_thread.html and I'm trying code like:
b := wx.NewPaintEvent()
f.GetEventHandler().QueueEvent(b)
instead of calling Refresh and Update but my wx.NewPaintEvent doesn't do anything. Maybe I'm making the wx.NewPaintEvent wrong? Or I'm adding it to the wrong EventHandler?

Answer 1

Generally speaking, doing anything with GUI objects from the non-main (i.e. not the one that initialized the library) thread is not supported by wxWidgets.
The usual workaround is to post an event to the main thread asking it to update the widget instead of doing it directly in the worker thread. In C++ this can be done easily and elegantly using CallAfter(), but I don't know enough about Go and wxGo to show you an example of doing it in this language.

Answer 2

author of wxGo fixed it:
https://github.com/dontpanic92/wxGo/issues/10
wx.Bind(f, wx.EVT_THREAD, func(e wx.Event) {
threadEvent := wx.ToThreadEvent(e)
the_gauge.SetValue(threadEvent.GetInt())
}, UPLOAD_WORKER_ID)
then in the thread:
threadEvent := wx.NewThreadEvent(wx.EVT_THREAD, UPLOAD_WORKER_ID)
threadEvent.SetInt(50)
f.QueueEvent(threadEvent)