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Details on Controls Properties

   

The Size of a Control

 

Introduction

The distance from the left border to the right border of a control is referred to as its Width property. In the same way, the distance from the top to the bottom borders of a control is its Height value. This can be illustrated as follows:

The location and dimension of a control

If you click a control's button on the Toolbox and click its parent window, the control assumes some default dimensions in the body of the parent.

Control Resizing

All graphical controls, including the form, can be resized using guiding mouse cursors. To resize a control, first select it. Except for the form, whenever a control is selected, there are eight handles around it. To resize the control, position your mouse on one of the handles. The mouse pointer will change, indicating in what direction you can move to resize the control.

Cursor Role
Moves the seized border in the North-West <-> South-East direction
Shrinks or heightens the control
Moves the seized border in the North-East <-> South-West direction
Narrows or enlarges the control


To resize the control by one grid unit, click one of the handles and drag in the desired location. Once satisfied, release the mouse.

To heighten or shrink a control by its lower border and one unit at a time, select the control, press and hold Shift. Then press the down arrow key as many times as necessary. Once satisfied, release the mouse and Shift.

To heighten or shrink a control by its lower border by small units, select the control, press and hold Ctrl and Shift. Then press the down arrow key as many times as necessary. Once satisfied, release the mouse and Ctrl and Shift.

The Bounding Rectangle of a Control

When a control has been added to a container, it occupies a Rectangle represented by the Bounds property. The syntax of this property is:

public:
    property Rectangle get_Bounds();
public:
    property void set_Bounds(Rectangle);

At any time, to get the location and the dimensions of a control, you can call its Bounds property, which produces a Rectangle value.

The Width and Height of a Control

Imagine you have added three controls to your form and, after spending some time designing them, they appear as follows:

The dimensions of the controls are not set professionally. As seen above, you can resize by dragging their borders but this might take a while if you want them to have the same width, the same height, or both the same height and width. The dimensions of a control or a group of controls are carried by a Size value.

At design time, to change the dimensions of a control, first click it. Then, in the Properties window, change the values of its Size property.

To change the dimensions of a group of controls, first select them. Then, in the Properties window, change the values of the Size field. The new value would be applied to all selected controls. Alternatively, the Form Designer provides tools to automatically do this for you.

To synchronize the widths of a group of controls, first select them. Then, on the Layout toolbar or on the Format group of the main menu, select:

Button Name Format
Make Same Width Make Same Width Make Same Size -> Width

Result: All controls, except for the base control (the control that has the dark handles), will be resized horizontally so they have the same width as the base control:

A form with some controls selected using a fake rectangle => A form where a group of controls has been configured to have the same width with controls selected using a fake rectangle
=> A form where a group of controls has been configured to have the same width with controls selected at random
A form with controls selected at random

To set the same height to a group of controls, first select them. Then, on the Layout toolbar or on the Format group of the main menu, select:

Button Name Format
Make Same Height Make Same Height Make Same Size -> Height

Result: All controls, except for the base control (the control that has the dark handles), will be resized vertically so they have the same height as the base control:

A form with some controls selected using a fake rectangle =>
A form with controls selected at random =>
=>

To set the same width and the same height to a group of controls, first select them. Then, on the Layout toolbar or on the Format group of the main menu, select:

Button Name Format
Make Same Size Make Same Size Make Same Size -> Both

Result: The Form Designer will calculate the sum of the heights of all controls and find their average height (AvgHeight). It will also calculate the sum of the widths of all controls and find their average width (AvgWidth). These averages will be applied to the height and the width respectively of each control:

=>
=>
=>
 

Practical LearningPractical Learning: Setting the Locations and Sizes of Controls

  1. Star Microsoft Visual C++
  2. To create a new application, on the main menu, click File -> New -> Project...
  3. In the Project Types list, click Visual C++ and, In the middle list, click Windows Forms Application
  4. In the Name box, replace the content with RectangleExercise1 and press Enter
  5. From the Toolbox and from what we learned in the previous lesson, add four labels, four text boxes, and two buttons to the form
  6. Based on what we have reviewed so far, design the form as follows:
     
    The Calculate Form
  7. To test the application, on the Standard toolbar, click the Start Debugging button Start Without Debugging
     
    The Calculate Application
  8. While the form is displaying, drag its right border to widen it. Also drag its bottom border to heighten it
     
    The form resized by the user
  9. Close the form and return to your programming environment

Run Time Controls Location and Dimensions

 

Introduction

If you position a (visual) control on a form, if the control is positioned on the top left section of the form, when the user resizes the form, the control's position would appear static, it would not move. This could be a concern if the control is positioned on the right, the bottom or the lower right sections of the form. When the user resizes the form, the control's position would not be updated. Sometimes you will want the control to have the same location and/or distance with regard to the bottom, the right, and/or the lower right corners of the form.

Control Anchoring

 The ability to manage a control or a group of controls' location and size when the use resizes it is done using the Anchor property:

The Anchor Property

The Anchor property is created from the AnchorStyles enumerator. By default, when you add a control to a form, it is “glued” to the top left corner of its container. You can also set the control's position with regards to its container's right and bottom borders. The Anchor property can be used to "glue" one border of a control to its parent using one of the following values:

Bottom: The control bottom border will be the same even if the parent is heighten or shrunk

Left: The control left border will be the same even if the parent is widened or narrowed


None: No anchoring is applied

Right: The control right border will be the same even if the parent is widened or narrowed

 


Top: The control top border will be the same even if the parent is heightened or shrunk

In the same way, you can combine Anchor values to "glue" one or more corners of a control to its parent when the parent is resized.

 
 
 

Practical LearningPractical Learning: Anchoring the Controls

  1. On the form, select the buttons on the right side:
     
  2. In the Properties window, click Anchor and click the arrow of its combo box
  3. Click the top vertical line and the right horizontal line. Click the left horizontal line to clear it:
     
  4. On the form, select all text boxes
  5. In the Properties window, click Anchor and click the arrow of its combo box. Click the right horizontal line and keep the others
     
    Anchor
  6. Execute the application
  7. Resize it horizontally and vertically to see the result
     
  8. Close the form and return to your programming environment

Control Docking

When a control is added to a host, depending on the control, it may be automatically positioned where the mouse landed. In some cases, you will want the control to be attached to a border or to a corner of its parent. This can be done using the Dock property:

Dock

This property is managed through the DockStyle enumerator. To use this property, click the control and, in the Properties window, click the arrow of the Dock field. You can then select one of the following values:

Bottom: The control will be attached to the bottom border of its parent:

Dock: Bottom A control docked bottom

Fill: The control will use the whole client area of its parent:

Left: The control will be attached to the left border of its parent:

Dock: Right A control docked right

None: The control will be kept where it was positioned on the parent:

Dock

Right: The control will be attached to the right border of its parent:

Dock

Top: The control will be attached to the top border of its parent:

Dock
 

Practical LearningPractical Learning: Docking a Control

  1. On the Toolbox, click Panel
  2. On the form, click and hold the mouse somewhere in the lower-left section. Then drag right and slightly up to draw it as follows (no need for precision):
     
  3. While the panel control is still selected, in the Properties window, click Dock and click the arrow of its combo box
  4. Select the box above None (to select Bottom)
     

Aesthetic Aspects of a Control

 

Background Color

Controls used on Microsoft Windows are painted using a color known as Control. If you don't like the default color that paints the background of a control, you can access the BackColor field of the Properties window:

Back Color

You can then select one of the preset colors from 3 windows represented with tabs.

Practical LearningPractical Learning: Changing the Background Color of a Control

  1. On the form, click the bottom panel
  2. In the Properties window, click BackColor and click its arrow
  3. Click the Custom tab and click the color at 3rd column - 2nd row:
     
    A control with a new background color
  4. Execute the application to test it
  5. Close the form and return to your programming environment

Background Image

Instead of a color, you may want to fill the control with a picture. To do this, you can access the control's BackgroundImage property. This provides an ellipsis button you can use to locate and select the desired picture.

Border Style

Some controls display a border when they are drawn and some others don't. Consider the following:

Some of these controls allow you to specify a type of border you want to show surrounding the controls. This characteristic is controlled by the BorderStyle property, which is based on BorderStyle enumerator. Its members are:

Value Example
Fixed3D
FixedSingle
None
 

API Characteristics of Controls

 

Tab Ordering

A user can navigate through controls using the Tab key. When that key has been pressed, the focus moves from one control to the next. By their designs, not all controls can receive focus and not all controls can participate in tab navigation. Even controls that can receive focus must be primarily included in the tab sequence.

At design time, the participation to tab sequencing is controlled by the Boolean TabStop property in the Properties window. Every visual control that can receive f aocus is already configured to have this property set to True. If you want to remove a control from this sequence, set its TabStop value to False.

If a control has the TabStop property set to True, to arrange the navigation order of controls, you have two main options. At design time, you can click a control on the form. Then, on the Properties window, change the value of its TabIndex field. The value must be a positive short integer.

The best and easiest way to arrange the tab sequence of controls is to manage it visually. To do this, first display the form. Then, on the main menu, click View. This causes a number to be positioned on every control of the form. Here is an example:

Tab Order

To arrange the sequence any way you like, click each control once in the desired order. Normally, static controls (such as the label, the picture box, the panel, etc) never receive focus when the application is running; therefore, you can skip such controls.

Practical LearningPractical Learning: Setting the Tab Order of Controls

  1. Click anywhere in the form
  2. On the main menu, click View -> Tab Order
  3. On the form, click, in the following order, the text box on the right side of Length, the text box on the right side of Height, the Calculate button, and the Close button
     
  4. Press Esc to dismiss the Tab Order tool
  5. On the form, click the text box on the right side of Perimeter:
  6. In the Properties window, set the TabStop to False
     
    Tab Stop
  7. In the same way, set the TabStop property of the text box on the right side of Area: to False
  8. Execute the application
  9. Press Tab a few times and observe the behavior
  10. Close the form and return to your programming environment

Flat Styles

Microsoft Windows XP added a new feature to the way some controls display or behave when the mouse passes over them, making the controls significantly attractive and enhanced. This feature is neither automatically applied on controls nor available on all controls. Therefore, before using it, you must first find out if the control you want to use it on support it. A control that supports this feature should have the FlatStyle property. This property provides the following values:

  • Flat: The button appears flat. When the mouse is over it, it becomes highlighted

  • Popup: The button appears flat. When the mouse is over it, the borders of the button are raised (if you have used WordPerfect, you may have seen this effect)

  • Standard: The buttons appears and behave like all regular buttons you have seen

  • System: The appearance of the button depends on the operating system using it

If the application will be run on Windows XP, you can use the System value of the FlatStyle property. To make this style work, call the Application.EnableVisualStyles() method in the Main() method as follows:

int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR    lpCmdLine,
                     int       nCmdShow)
{
    System::Threading::Thread::CurrentThread->ApartmentState = 
		System::Threading::ApartmentState::STA;
    Application::EnableVisualStyles();

    Application::Run(new Form1());
    return 0;
}

Practical LearningPractical Learning: Using Flat Styles

  1. On the form, select both the Calculate and the Close buttons
  2. In the Properties window, click FlatStyles and click the arrow of its combo box
  3. Select System
  4. In the Solution Explorer, expand the Source Files node if necessary. Double-click Form1.cpp
  5. Change the WinMain() function as follows:
    int APIENTRY WinMain(HINSTANCE hInstance,
                         HINSTANCE hPrevInstance,
                         LPSTR    lpCmdLine,
                         int       nCmdShow)
    {
        System::Threading::Thread::CurrentThread->ApartmentState = 
    	System::Threading::ApartmentState::STA;
    	
        Application::EnableVisualStyles();
    
        Application::Run(new Form1());
        return 0;
    }
  6. Execute the application
  7. Close the form and return to your programming environment

Control's Visibility

A control is referred to as visible if it can be visually located on the screen. A user can use a control only if he or she can see it. As a programmer, you have the role of deciding whether a control must be seen or not and when. The visibility of an object is controlled by the its Visible property. This is a Boolean property.

At design time, when you add a control to a parent, it is visible by default. This is because its Visible property is set to True in the Properties window. In the same way, if you programmatically create a control, by default, it is made visible once you add it to its parent's Controls property.

If you don't want a control to primarily appear when the form comes up, you can either set its Visible property to False or set its parent's visible property to False. Equivalently, at run time, to hide a control, assign a False value to either its Visible property or its parent's Visible property. Keep in mind that when a parent gets hidden, it also hides its children. On the other hand, a parent can be made visible but hide one or some of its children.

To check whether a control is visible at one time, apply a conditional statement (if or while) to its Visible property and check whether its value is True or False. In the following example, when the user clicks a button named button1, a text box named textBox1 gets hidden.

Control's Availability

For the user to use a control, it must allow operations on it. For example, if a control is supposed to receive text, the user can enter characters in it only if this is made possible. To make a control available to the user, the object must be enabled. The availability of an object is controlled by the Boolean Enabled property.

By default, after adding a control to a form, it is enabled and its Enabled property in the Properties window is set to True. An enabled control displays its text or other characteristics in their normal settings. If you want to disable a control, set its Enabled property to False. In the following picture, a text box and a button are disabled:

Enabled

To find out whether a control is enabled or not, check its Enabled property state.

Allowing Drag n' Drop Operations

Drag n' drop is the ability to drag an object or text from one location or object to another. This is a significant operation in computer use. Although Microsoft Windows fully supports drag n' drop operations, because the operating system cannot predict how the operations should be carried, you must write code.

Various controls support drag n' drop operations. While most controls support them, it is not always realistic to implement the operations on every control. This means that you will have to decide when, how, and what controls of your application will need to allow the user do drag what and drop it where.

A control that allows drag n' drop operations is equipped with a Boolean property named AllowDrop. When you set this property to true, it means the user can either drag something from it or drop something on it. After setting this property, you must write code. We will see examples in future lessons.

 
 
   
 

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