Dialogs

In this part of the IronPython Mono Winforms tutorial, we will talk about dialogs.

Dialog windows or dialogs are an indispensable part of most modern GUI applications. A dialog is defined as a conversation between two or more persons. In a computer application a dialog is a window which is used to "talk" to the application. A dialog is used to input data, modify data, change the application settings etc. Dialogs are important means of communication between a user and a computer program.

There are essentially two types of dialogs. Predefined dialogs and custom dialogs.

FolderBrowserDialog

This dialog prompts the user to select a folder.

#!/usr/bin/ipy

import clr
clr.AddReference("System.Windows.Forms")
clr.AddReference("System.Drawing")

from System.Windows.Forms import Application, Form, StatusBar
from System.Windows.Forms import ToolBar, ToolBarButton, FolderBrowserDialog
from System.Windows.Forms import DialogResult


class IForm(Form):

    def __init__(self):
        self.Text = "FolderBrowserDialog"
 
        toolbar = ToolBar()
        toolbar.Parent = self
        openb = ToolBarButton()

        self.statusbar = StatusBar()
        self.statusbar.Parent = self

        toolbar.Buttons.Add(openb)
        toolbar.ButtonClick += self.OnClicked

        self.CenterToScreen()


    def OnClicked(self, sender, event):
        dialog = FolderBrowserDialog()

        if (dialog.ShowDialog(self) == DialogResult.OK):
            self.statusbar.Text = dialog.SelectedPath
       

Application.Run(IForm())

We have a toolbar and one toolbar button. By clicking on the button, the FolderBrowserDialog appears on the screen. The name of the selected folder is shown in the statusbar.

dialog = FolderBrowserDialog()

The FolderBrowserDialog is created.

if (dialog.ShowDialog(self) == DialogResult.OK):
    self.statusbar.Text = dialog.SelectedPath  

The ShowDialog() method shows the dialog on the screen. If we click on the OK button of the dialog, the selected directory path is shown on the statusbar.

ColorDialog

This dialog displays available colours along with controls that enable the user to define custom colours.

#!/usr/bin/ipy

import sys
import clr
clr.AddReference("System.Windows.Forms")
clr.AddReference("System.Drawing")

from System.Windows.Forms import Application, Form, ToolBar
from System.Windows.Forms import ToolBarButton, ControlStyles, ColorDialog
from System.Windows.Forms import DialogResult
from System.Drawing import Size, Color, SolidBrush, Rectangle

RECT_WIDTH  = 100
RECT_HEIGHT = 100

class IForm(Form):

    def __init__(self):
        self.Text = "ColorDialog"

        self.color = Color.Blue

        toolbar = ToolBar()
        toolbar.Parent = self
        openb = ToolBarButton()

        toolbar.Buttons.Add(openb)
        toolbar.ButtonClick += self.OnClicked

        self.LocateRect()

        self.SetStyle(ControlStyles.ResizeRedraw, True)
        self.Paint += self.OnPaint
 
        self.CenterToScreen()
    
    
    def OnPaint(self, event):
        g = event.Graphics
        self.LocateRect()
        brush = SolidBrush(self.color)
        g.FillRectangle(brush, self.r)
    

    def OnClicked(self, sender, events):
        dialog = ColorDialog()

        if (dialog.ShowDialog(self) == DialogResult.OK):
            self.color = dialog.Color
            self.Invalidate()
       
    def LocateRect(self):
        x = (self.ClientSize.Width - RECT_WIDTH) / 2
        y = (self.ClientSize.Height - RECT_HEIGHT) / 2
        self.r = Rectangle(x, y, RECT_WIDTH, RECT_HEIGHT)
    
    
Application.Run(IForm())

In this code example, we use the ColorDialog to choose a colour for a rectangle that is located in the middle of the form control.

self.color = Color.Blue

At the beginning, the colour of the rectangle is blue. We use the self.color variable to determine the colour of the rectangle.

dialog = ColorDialog()

The ColorDialog is created.

if (dialog.ShowDialog(self) == DialogResult.OK):
    self.color = dialog.Color
    self.Invalidate()

The code shows the colour dialog. If we click on the OK button, we get the selected colour and call the Invalidate() method. The method invalidates the entire surface of the control and causes the control to be redrawn. The result is that the rectangle is drawn with a new colour value.

FontDialog

The FontDialog is used to select fonts.

#!/usr/bin/ipy

import clr
clr.AddReference("System.Windows.Forms")
clr.AddReference("System.Drawing")

from System.Windows.Forms import Application, Form, StatusBar, Label
from System.Windows.Forms import ToolBar, ToolBarButton, FontDialog
from System.Windows.Forms import DialogResult

class IForm(Form):

    def __init__(self):
        self.Text = "FolderBrowserDialog"
 
        self.text = Label()
        self.text.Parent = self
        self.text.Text = "Winforms tutorial"

        self.LocateText()
 
        toolbar = ToolBar()
        toolbar.Parent = self
        openb = ToolBarButton()

        toolbar.Buttons.Add(openb)
        toolbar.ButtonClick += self.OnClicked

        self.text.AutoSize = True
        self.Resize += self.OnResize
 
        self.CenterToScreen()
    

    def OnResize(self, sender, event):
        self.LocateText()


    def LocateText(self): 
        self.text.Top = (self.ClientSize.Height - self.text.Height) / 2
        self.text.Left = (self.ClientSize.Width - self.text.Width) / 2
    

    def OnClicked(self, sender, event):

        dialog = FontDialog()

        if (dialog.ShowDialog(self) == DialogResult.OK):
           self.text.Font = dialog.Font
           self.LocateText()
       

Application.Run(IForm())

We draw some text in the middle of the form control. We use the font dialog to change font for this text.

dialog = FontDialog()

FontDialog is created.

if (dialog.ShowDialog(self) == DialogResult.OK):
    self.text.Font = dialog.Font
    self.LocateText()

When we click on the OK button, we set a newly selected font for the Label control. Because the size of the text changes with different fonts, we must call the LocateText() method, which locates the text in the middle of the form control.

OpenDialog

This dialog is used to open files.

#!/usr/bin/ipy

import clr
clr.AddReference("System.Windows.Forms")
clr.AddReference("System.Drawing")

from System.Windows.Forms import Application, Form, TextBox
from System.Windows.Forms import ToolBar, ToolBarButton, OpenFileDialog
from System.Windows.Forms import DialogResult, ScrollBars, DockStyle


class IForm(Form):

    def __init__(self):
        self.Text = "OpenDialog"
 
        toolbar = ToolBar()
        toolbar.Parent = self
        openb = ToolBarButton()
        

        self.textbox = TextBox()
        self.textbox.Parent = self
        self.textbox.Multiline = True
        self.textbox.ScrollBars = ScrollBars.Both
        self.textbox.WordWrap = False
        self.textbox.Parent = self
        self.textbox.Dock = DockStyle.Fill
      

        toolbar.Buttons.Add(openb)
        toolbar.ButtonClick += self.OnClicked


        self.CenterToScreen()

    def OnClicked(self, sender, event):
        dialog = OpenFileDialog()
        dialog.Filter = "C# files (*.cs)|*.cs"

        if dialog.ShowDialog(self) == DialogResult.OK:
            f = open(dialog.FileName)
            data = f.read()
            f.Close()
            self.textbox.Text = data
       

Application.Run(IForm())

We use the OpenDialog control to open C# source files. We have a TextBox control, where we display the file.

dialog = OpenFileDialog()

The OpenDialog is created.

dialog.Filter = "C# files (*.cs)|*.cs"

We set the Filter property to C# source files. Only C# files can be chosen with this dialog instance.

if dialog.ShowDialog(self) == DialogResult.OK:
    f = open(dialog.FileName)
    data = f.read()
    f.Close()
    self.textbox.Text = data

After clicking OK, we read the contents of the chosen file and put it into the TextBox control.

In this part of the IronPython Mono Winforms tutorial, we showed various dialogs.