Notepad++ Memory Leak: BabyGrid.cpp's Font Issue

Hey guys, let's dive into a sneaky little bug that's been hanging out in Notepad++, specifically in the BabyGrid.cpp file. This issue involves a memory leak related to how fonts are handled within the "Shortcut Mapper" window. It's not a catastrophic error, but it's the kind of thing that, if left unchecked, can lead to performance degradation over time. We'll break down the problem, how to reproduce it, and what's supposed to happen versus what actually happens.

The Core of the Problem: Font Creation and Destruction

The heart of the issue lies within the GridProc function, which is the window procedure responsible for handling messages related to the BabyGrid control. When the "Shortcut Mapper" window is created (via the WM_CREATE message), three fonts are created: g_hfontbody, g_hfontheader, and g_hfonttitle. These fonts are used to render text within the grid control, providing the visual elements of the shortcut mapper interface. The code snippet responsible for creating these fonts is provided below, and can be found in the GridProc function, in the WM_CREATE section. The code initializes and configures these fonts, setting their size, weight, and typeface. This is where the resource allocation begins, setting up the visual appearance of the text within the shortcut mapper. Specifically, they set font sizes, weights (like bold), and the font family.

LRESULT CALLBACK GridProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
        case WM_CREATE:
        {
            CREATESTRUCT* lpcs = (LPCREATESTRUCT)lParam;
            HINSTANCE hInst = lpcs->hInstance;
            int BG_GridIndex = AddGrid(GetMenu(hWnd));

            if (CountGrids() == 1)
            {
                g_hfontbody = CreateFont(16, 0, 0, 0,
                    100,
                    FALSE,
                    FALSE, FALSE, DEFAULT_CHARSET,
                    OUT_DEFAULT_PRECIS,
                    CLIP_DEFAULT_PRECIS,
                    0,
                    0,
                    L"MS Shell Dlg");
                g_hfontheader = CreateFont(18, 0, 0, 0, FW_HEAVY, FALSE, FALSE, FALSE, DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS, 0, 0, L"MS Shell Dlg");
                g_hfonttitle = CreateFont(20, 0, 0, 0, FW_HEAVY, FALSE, FALSE, FALSE, DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS, 0, 0, L"MS Shell Dlg");
            }
        }
    }
}

Later, when the window is destroyed (WM_DESTROY message), the code attempts to delete these fonts to free up the memory. However, there is a flaw in the conditional statement. The code is designed to only delete the fonts if CountGrids() == 0, but this condition is never met when the shortcut mapper window is closed. This means the DeleteObject calls, which are essential for releasing the memory occupied by the fonts, are skipped. This crucial omission is the root of the memory leak. The WM_DESTROY part of the GridProc function, along with the error can be seen below.

LRESULT CALLBACK GridProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
        case WM_DESTROY:
        {
            if (CountGrids() == 0)
            {
                DeleteObject(g_hfontbody);
                DeleteObject(g_hfontheader);
                DeleteObject(g_hfonttitle);
            }
        }
    }
}

Reproducing the Memory Leak: A Step-by-Step Guide

Now, let's see how you can experience this memory leak firsthand. The process is simple and straightforward, allowing anyone to confirm the issue. By repeating these steps, you can observe the font handles accumulating over time, illustrating the memory leak's persistence. Keep in mind, this isn't an immediate crash-inducing problem, but rather a slow drain on resources. It will subtly diminish your system's performance as you use Notepad++ more and more. The beauty of this bug is that it can be easily tested. Follow these simple steps to reproduce the memory leak.

1. Open the "Shortcut Mapper" Window: In Notepad++, navigate to the "Settings" menu, then select "Shortcut Mapper". This action triggers the creation of the BabyGrid window and, consequently, the font objects.
2. Close the "Shortcut Mapper" Window: Close the window by clicking the close button (X). This is where the bug occurs. The window attempts to deallocate the font resources, but it fails due to the conditional check.
3. Repeat: Repeat steps 1 and 2 multiple times. Each time you open and close the "Shortcut Mapper", the three fonts are created, but not released. Over time, the number of these unreleased font objects increases, leading to memory consumption. The more you repeat the process, the more significant the memory leak becomes.

The Expected Behavior vs. Reality

So, what should happen, and what actually happens? The expected behavior is that when the "Shortcut Mapper" window is closed, the fonts created within GridProc should be deleted using DeleteObject. This would free the memory allocated for the font objects, preventing any leaks. This should happen immediately after the window is destroyed. The code attempts to do this, but the condition if (CountGrids() == 0) prevents it from working correctly. The reality is that the fonts are not deleted when the window is closed. The DeleteObject calls are bypassed because CountGrids() remains 1. The three fonts g_hfontbody, g_hfontheader, and g_hfonttitle remain in memory until the entire Notepad++ application is closed. Every time you open and close the "Shortcut Mapper" window, the three fonts are created, but not released. This accumulation of unreleased font objects leads to the memory leak.

Consequences and Why It Matters

While this memory leak might seem minor, it's essential to understand its potential consequences. As the fonts accumulate, they consume system resources, particularly memory. Over extended periods of use, this can lead to:

• Decreased Performance: As the system runs out of memory, it may start swapping data to disk, which is significantly slower than accessing RAM. This can cause Notepad++ and other applications to slow down.
• Increased Resource Consumption: The memory leak increases the overall memory footprint of Notepad++, consuming more resources than necessary.
• Potential Instability: Although less likely in this case, continuous memory leaks can, in extreme scenarios, lead to instability or crashes. This can make the software less reliable and cause data loss.

Debug Information

There is no specific debug information needed to showcase this bug because of its simplicity. The issue can be observed using any debugging tool that monitors resource allocation and deallocation, or simply by repeatedly opening and closing the "Shortcut Mapper" window and monitoring the system's memory usage.

Closing Thoughts

So, there you have it. A small bug with potentially big implications. Remember, keeping software clean and efficient is crucial for a smooth user experience. If you're a Notepad++ user, keep an eye on this, and if you're a developer, maybe lend a hand to fix it! It's always a good idea to stay updated on software updates. This will help to fix any of the bugs that are present. This will ensure that you have the best user experience.

For more information about Notepad++ and other software bugs, check out some of the resources available online. You can find various forums and blogs. You can also find technical documentation that will help with the process. The Notepad++ Community Forum is a great resource to find more information about this issue, and to keep an eye on a future fix.

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