[BUG] New version display window error

[suoyukii]

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x20 pc=0x5ac794]

goroutine 1 [running, locked to thread]:
github.com/lxn/walk.CreateLayoutItemsForContainerWithContext(0x92e1a0, 0xc000186800, 0xc000184dc0, 0xa0802, 0x0)
        C:/Users/12526/go/src/github.com/lxn/walk/layout.go:61 +0x504
github.com/lxn/walk.CreateLayoutItemsForContainer(0x92e1a0, 0xc000186800, 0x0, 0x338)
        C:/Users/12526/go/src/github.com/lxn/walk/layout.go:49 +0xbb
github.com/lxn/walk.(*FormBase).startLayout(0xc000186800, 0x70818)
        C:/Users/12526/go/src/github.com/lxn/walk/form.go:726 +0x11a
github.com/lxn/walk.(*FormBase).WndProc(0xc000186800, 0x70818, 0x47, 0x0, 0x124fdd0, 0x0)
        C:/Users/12526/go/src/github.com/lxn/walk/form.go:818 +0x7bc
github.com/lxn/walk.(*MainWindow).WndProc(0xc000186800, 0x70818, 0x47, 0x0, 0x124fdd0, 0x28)
        C:/Users/12526/go/src/github.com/lxn/walk/mainwindow.go:233 +0x76
github.com/lxn/walk.defaultWndProc(0x70818, 0x47, 0x0, 0x124fdd0, 0x0)
        C:/Users/12526/go/src/github.com/lxn/walk/window.go:1989 +0xd7
syscall.Syscall(0x7ffe6b063d60, 0x2, 0x70818, 0x8, 0x0, 0x0, 0x0, 0x0)
        c:/go/src/runtime/syscall_windows.go:184 +0xea
github.com/lxn/win.ShowWindow(0x70818, 0x8, 0xa0802)
        C:/Users/12526/go/src/github.com/lxn/win/user32.go:3186 +0x6a
github.com/lxn/walk.setWindowVisible(...)
        C:/Users/12526/go/src/github.com/lxn/walk/window.go:1249
github.com/lxn/walk.(*WindowBase).SetVisible(0xc000186800, 0x43b1b01)
        C:/Users/12526/go/src/github.com/lxn/walk/window.go:1213 +0x72
github.com/lxn/walk.(*MainWindow).SetVisible(0xc000186800, 0x92b801)
        C:/Users/12526/go/src/github.com/lxn/walk/mainwindow.go:141 +0x41
github.com/lxn/walk.(*FormBase).Show(0xc000186800)
        C:/Users/12526/go/src/github.com/lxn/walk/form.go:603 +0xde

[suoyukii]

@lxn

[suoyukii]

package main

import (
    "syscall"

    "github.com/lxn/walk"
)

func GetSystemMetrics(nIndex int) int {
    ret, _, _ := syscall.NewLazyDLL(`User32.dll`).NewProc(`GetSystemMetrics`).Call(uintptr(nIndex))
    return int(ret)
}

func main() {
    window, _ := walk.NewMainWindow()
    window.SetWidth(400)
    window.SetHeight(400)
    window.SetX((GetSystemMetrics(0) - window.Width()) / 2)
    window.SetY((GetSystemMetrics(1) - window.Height()) / 2)
    window.Show()
    window.Run()
}

[lxn]

Thanks for reporting. This should be fixed by https://github.com/lxn/walk/commit/a8335f0ed5c41e27807bb706c61583ecefdcd2a5.

[suoyukii]

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x20 pc=0x5acd10]

goroutine 1 [running, locked to thread]:
github.com/lxn/walk.CreateLayoutItemsForContainerWithContext(0x92fa60, 0xc00017e800, 0xc000045a90, 0x8062c, 0x0)
        C:/Users/12526/go/src/github.com/lxn/walk/layout.go:65 +0x520
github.com/lxn/walk.CreateLayoutItemsForContainer(0x92fa60, 0xc00017e800, 0x0, 0x338)
        C:/Users/12526/go/src/github.com/lxn/walk/layout.go:49 +0xbb
github.com/lxn/walk.(*FormBase).startLayout(0xc00017e800, 0x90624)
        C:/Users/12526/go/src/github.com/lxn/walk/form.go:726 +0x11a
github.com/lxn/walk.(*FormBase).WndProc(0xc00017e800, 0x90624, 0x47, 0x0, 0x124fdd0, 0x0)
        C:/Users/12526/go/src/github.com/lxn/walk/form.go:818 +0x7bc
github.com/lxn/walk.(*MainWindow).WndProc(0xc00017e800, 0x90624, 0x47, 0x0, 0x124fdd0, 0x28)
        C:/Users/12526/go/src/github.com/lxn/walk/mainwindow.go:233 +0x76
github.com/lxn/walk.defaultWndProc(0x90624, 0x47, 0x0, 0x124fdd0, 0x0)
        C:/Users/12526/go/src/github.com/lxn/walk/window.go:1989 +0xd7
syscall.Syscall(0x7fff26ee3d60, 0x2, 0x90624, 0x8, 0x0, 0x0, 0x0, 0x0)
        c:/go/src/runtime/syscall_windows.go:184 +0xea
github.com/lxn/win.ShowWindow(0x90624, 0x8, 0x8062c)
        C:/Users/12526/go/src/github.com/lxn/win/user32.go:3186 +0x6a
github.com/lxn/walk.setWindowVisible(...)
        C:/Users/12526/go/src/github.com/lxn/walk/window.go:1249
github.com/lxn/walk.(*WindowBase).SetVisible(0xc00017e800, 0x12a6101)
        C:/Users/12526/go/src/github.com/lxn/walk/window.go:1213 +0x72
github.com/lxn/walk.(*MainWindow).SetVisible(0xc00017e800, 0x92d001)
        C:/Users/12526/go/src/github.com/lxn/walk/mainwindow.go:141 +0x41
github.com/lxn/walk.(*FormBase).Show(0xc00017e800)
        C:/Users/12526/go/src/github.com/lxn/walk/form.go:603 +0xde

[suoyukii]

• Set the width and height of the window to be behind the Show() so that errors will not be reported.

  window.SetLayout(walk.NewGridLayout())
  
  // Set window position
  window.SetX((sys_width - window_width) / 2)
  window.SetY((sys_height - window_height) / 2)
  
  // Maximum height of container
  max_y := len(btn_list) / max_x
  if len(btn_list)%max_x != 0 {
      max_y += 1
  }
  
  // Add button
  for _, val := range btn_list {
      HD_Button(val)
  }
  
  // Window size change event
  window.SizeChanged().Attach(func() {
      btn_len := window.Children().Len()
      i := 0
      btn_w := window.ClientBounds().Width / max_x
      btn_h := window.ClientBounds().Height / max_y
      x := 0
      y := -btn_h
      rect := walk.Rectangle{X: x, Y: y, Width: btn_w, Height: btn_h}
      for ; i < btn_len; i++ {
          if i%max_x == 0 {
              rect.X = 0
              rect.Y += btn_h
          }
          window.Children().At(i).SetBounds(rect)
          rect.X += btn_w
      }
  })
  
  // Display window
  window.Show()
  
  // Set width and height
  window.SetWidth(window_width)
  window.SetHeight(window_height)

[suoyukii]

What if I prefer to use my own Layout? I don't really want to use the layout set up by the system.

[lxn]

Not sure if this is still possible. You may have to implement walk.Layout and walk.ContainerLayoutItem. Or wait until I restore support for custom layouts.