Create a not resizable window with XLib

3 min read 06-10-2024

Creating a Not-Resizable Window with XLib: A Guide to Fixed-Size Applications

The X Window System, often referred to as Xlib, provides the foundation for graphical user interfaces on Linux and other Unix-like systems. While it offers a highly customizable environment for creating windows, sometimes we need to enforce a fixed size for our application. This article will guide you through creating a non-resizable window using XLib.

Understanding the Problem

Imagine you're developing a specialized tool that requires a specific layout and precise dimensions. A user accidentally resizing the window could disrupt the functionality or even cause visual glitches. In such cases, we need to prevent the window from being resized.

Setting the Stage: The Code

Let's start with a basic XLib window creation example, which we'll modify to make it non-resizable.

#include <X11/Xlib.h>
#include <X11/Xutil.h>

int main() {
    Display *display;
    Window window;
    int screen;

    // Connect to the X server
    display = XOpenDisplay(NULL);
    if (display == NULL) {
        fprintf(stderr, "Error: Cannot connect to X server\n");
        exit(1);
    }

    // Get the default screen
    screen = DefaultScreen(display);

    // Create a simple window
    window = XCreateSimpleWindow(display, RootWindow(display, screen),
                                 10, 10, 300, 200, 1, BlackPixel(display, screen),
                                 WhitePixel(display, screen));

    // Set window attributes
    XSetWindowAttributes attributes;
    attributes.override_redirect = False; // Ensure we can use decorations
    attributes.event_mask = ExposureMask | KeyPressMask; 
    XChangeWindowAttributes(display, window, CWOverrideRedirect | CWEventMask, &attributes);

    // Map the window
    XMapWindow(display, window);

    // Event loop
    XEvent event;
    while (1) {
        XNextEvent(display, &event);
        switch (event.type) {
            case Expose:
                // Handle window exposure
                break;
            case KeyPress:
                // Handle key presses
                break;
        }
    }

    XCloseDisplay(display);
    return 0;
}

This code creates a basic window with a size of 300x200 pixels.

The Key to Non-Resizability: Window Attributes

To prevent resizing, we need to modify the window's attributes using XChangeWindowAttributes(). Specifically, we'll modify the WM_NORMAL_HINTS property, which informs the window manager about the window's size and resize behavior.

// ... (rest of the code)

// Modify WM_NORMAL_HINTS to prevent resizing
XSizeHints *size_hints = XAllocSizeHints();
size_hints->flags = PMinSize | PMaxSize;
size_hints->min_width = 300;
size_hints->min_height = 200;
size_hints->max_width = 300;
size_hints->max_height = 200;
XSetWMNormalHints(display, window, size_hints);
XFree(size_hints);

// ... (rest of the code)

In this code:

XAllocSizeHints() allocates memory for the XSizeHints structure.
PMinSize and PMaxSize flags indicate that we're setting minimum and maximum dimensions.
min_width, min_height, max_width, and max_height define the fixed dimensions for the window.

Putting It All Together

Combining these changes, the complete code for creating a non-resizable window with XLib is:

#include <X11/Xlib.h>
#include <X11/Xutil.h>

int main() {
    // ... (code from the previous example)

    // Modify WM_NORMAL_HINTS to prevent resizing
    XSizeHints *size_hints = XAllocSizeHints();
    size_hints->flags = PMinSize | PMaxSize;
    size_hints->min_width = 300;
    size_hints->min_height = 200;
    size_hints->max_width = 300;
    size_hints->max_height = 200;
    XSetWMNormalHints(display, window, size_hints);
    XFree(size_hints);

    // ... (rest of the code)
}

Now, when you run this code, the resulting window will be fixed at 300x200 pixels and users won't be able to resize it.

Important Notes:

Window Manager Compatibility: While this approach works for many window managers, some might have their own resizing policies. In rare cases, you might need to use additional techniques or workarounds.
Override Redirect: If you set override_redirect to True, the window manager will not handle the window's decorations or resizing. This can create a simpler window but may affect its appearance and behavior.

Additional Resources

For a deeper understanding of XLib and window management concepts, explore the following resources:

By understanding these principles and implementing the correct XLib functions, you can create custom, non-resizable windows that meet the specific requirements of your application.