SelectObject

Function: SelectObject

Syntax:

HGDIOBJ SelectObject(HDC hdc, HGDIOBJ hgdiobj);

Parameters:

The SelectObject function selects an object into the specified device context (DC). A device context is a data structure that contains information about the drawing attributes of a physical or virtual device.

Description

This function returns the handle to the object that was previously selected into the specified device context. This handle can be used to restore the original object later.

The objects that can be selected into a device context include:

Pens
Brushes
Fonts
Bitmaps
Palettes
Regions

When you select an object into a device context, the previous object of the same type is returned. It is important to save this handle and restore the original object when you are finished with the new one to avoid resource leaks and unexpected behavior.

Parameters

Parameter	Type	Description
`hdc`	`HDC`	A handle to the device context.
`hgdiobj`	`HGDIOBJ`	A handle to the object to be selected into the DC. This handle is obtained by calling a function such as `CreatePen`, `CreateSolidBrush`, `CreateFont`, `CreateBitmap`, or `LoadBitmap`.

Return Value

Type	Description
`HGDIOBJ`	If the function succeeds, the return value is a handle to the object that was previously selected into the specified device context. This handle can be used to restore the original object using `SelectObject`. If the function fails, the return value is `NULL`.

Example Usage

The following code snippet demonstrates how to select a new brush into a device context and then restore the original brush:


// Assume hdc is a valid device context handle
HDC hdc = GetDC(NULL);
HGDIOBJ hOldBrush = NULL;
HBRUSH hNewBrush = CreateSolidBrush(RGB(255, 0, 0)); // Red brush

if (hNewBrush != NULL) {
    // Select the new brush and save the old one
    hOldBrush = SelectObject(hdc, hNewBrush);

    // ... Perform drawing operations using the new red brush ...

    // Restore the original brush
    if (hOldBrush != NULL) {
        SelectObject(hdc, hOldBrush);
    }
    // Delete the new brush
    DeleteObject(hNewBrush);
}

// Release the device context
ReleaseDC(NULL, hdc);

Remarks

Always remember to restore the original object selected into the DC. Failure to do so can lead to resource leaks and corrupted graphics states.

The SelectObject function can be used to select various GDI objects, including pens, brushes, fonts, and bitmaps.