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4198 :: Need some guidance in win32 GUI programming.

• kcvinu (orginal) [2018-09-15T22:01:00+02:00] view original

  Hi all,

  I am practising nim by writing a gui library based on win32 api. So far so good. I have a working model now. But i am seeking more better method to make this lib stronger and better.

  This is my current scenario. Pseudocode;

  1. Create a type named "eventArgs".

     Members -

     1. uMsg = message in wndproc
     2. wHandle = hWnd in wndproc
     3. wParam = wParam in wndproc
     4. lParam = lParam in wndproc

  2. Create a type for a function pointer. We can call this "fnPtr"
  3. Create a global var in type eventArgs
  4. Create a local var in type fnPtr

  5. Create a tuple type named winData.

     Members -

     [caption : string,

     xPos : int32, yPos : int32, width : int32, height : int32, style : DWORD, exStyle : DWORD, parent : HWND]

  6. Create a type named winApp

     Members -

     config : winData wHandle : HWND proc - createGui* proc - showGui* proc - appMainLoop*

  7. In winApp's constructor, i init all the members in config. So now config's members have some initial values. Besides that, i am taking a function pointer as argument of this constructor.
  8. Then i created a button type. It's constructor take a HWND as parameter. It is the parent of the button.
  9. This lib has a global WndProc function. In that function, the function pointer(fnPtr) will be called.

  So, this is the strategy of my lib right now. Now, my question is, how can i improve this ? I would like to eliminate the need of single function and divide the functionality into multiple functions like "formCreate", "button1Click".

  This is my WndProc function in Module1

  proc WndProc( hwnd: HWND, message: UINT, wParam: WPARAM, lParam: LPARAM): LRESULT {.stdcall.} =
      
      eArgs.uMsg = message  # this eArgs is global.
      eArgs.wHandle = hwnd
      eArgs.lParam = lParam
      eArgs.wParam = wParam
      result = byPassProc()
      
      case message
          of WM_DESTROY:
              PostQuitMessage(0)
              return 0
          else:
              return DefWindowProc(hwnd, message, wParam, lParam)
  Run

  And this is the code from Module2

  import winim/lean
  import "Module1.nim"
  
  
  proc myCallBack() : LRESULT    # forward declaration
  var mApp = newWinApp(myCallBack)   # this constructor call will register this function in WndProc
  
  mApp.config.caption = "My New Window"    #some tweaks.
  let wHwn =  mApp.createGui()    # this proc will create a gui and return it's hwnd
  
  var btn = newButton(wHwn)    # button type constructor. This will take the parent handle as parameter.
  btn.config.caption = "Click Me"   # some tweaks
  btn.config.xPos = 200
  btn.config.yPos = 100
  discard btn.createButton()  #creating the button.
  
  mApp.ShowGui( )   # Displaying the gui
  mApp.appMainLoop()  # Entering into the main loop.
  
  proc myCallBack() : LRESULT =  #Here comes all the actions of this gui. I have simplified this as much i can.
      case eArgs.uMsg
          of WM_CREATE :
              echo "Window just Created"
          of WM_LBUTTONDOWN :
              msgBox("You clicked on Window")
          of WM_COMMAND :
              if eArgs.lParam == btn.bHandle :
                  msgBox("You clicked on Button")
          else :
              return 0
  Run

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