Smooth window resizing in Windows (using Direct2D 1.1)? - c++

Question

It annoys me that the resizing of windows in Windows is not as "smooth" as it I'd like it to be (this is the case with Windows programs in general, not just my own. Visual Studio is a good example). It makes the OS and its programs feel "flimsy" and "cheap" (yes, I care about how programs and user interfaces feel, in the same way I care about the sound and feel of closing a car door. It's a reflection of build quality), which in my view affects the overall UX and ultimately the perception of the brand.
The redrawing of window contents simply does not keep up with mouse movement during resize. Whenever I resize a window, there is a "stuttering" / "flickering" effect, seemingly due to the previous-size-contents of the window being redrawn in the new, resized window frame before the new, resized contents are drawn.
I am building a Win32 application (x64) that uses Direct2D 1.1 to draw its UI, and given the speed of Direct2D, i think it should be unnecessary to suffer such artifacts in an OS in 2014. I am on Windows 8.1 myself, but targeting Windows 7 and up with this application.
The "previous size" effect is especially discernible when maximizing a small window (since the difference in window size is sufficiently great to easily contrast the image of the old content as it flashes briefly in the upper left corner of the larger window with the new content subsequently being painted over it).
This is what appears to be going on:
(Let's say there's a fully rendered window on screen, size 500 x 500 pixels).
I maximize the window:
The window frame is maximized
The old 500 x 500 content is drawn in the new frame, before..
..the maximized window is repainted with properly sized content.
I'm wondering if there's any way to mitigate this (i.e. get rid of step 4) - via intercepting a Windows Message, for example - and avoid the window being repainted at the new size with the old content before the final re-rendering of the new content happens. It's like Windows does the window redrawing itself, using whatever graphics it already has available, BEFORE it bothers to ask me to provide updated content with a WM_PAINT message or similar.
Can it be done?
Edit: It seems that WM_WINDOWPOSCHANGING / WM_SIZING provides "early access" to the new size data, but I still haven't managed to suppress the painting of the old content.
My WndProc looks like this:
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_ERASEBKGND:
return 1;
case WM_PAINT:
PAINTSTRUCT ps;
BeginPaint(hWnd, &ps);
D2DRender();
EndPaint(hWnd, &ps);
return 0;
case WM_SIZE:
if (DeviceContext && wParam != SIZE_MINIMIZED)
{
D2DResizeTargetBitmap();
D2DRender();
}
return 0;
case WM_DISPLAYCHANGE:
D2DRender();
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hWnd, message, wParam, lParam);
}
The window does not have CS_HREDRAW or CS_VREDRAW set. The swapchain is double buffered and the Present call is made with SyncInterval = 0.
I am aware that recreating the swapchain buffers every time the window size changes does create some overhead compared to plain redrawing on a static window surface. However, the "stuttering" is not caused by that, as it happens even when buffer resizing is disabled and existing window contents are simply scaled during window resizing (although that does make it keep up better with mouse movement).

Answer 1

There is a way to prevent the needless BitBlt mentioned in step 4 above.
Until Windows 8 it could be done either by creating your own custom implementation of WM_NCCALCSIZE to tell Windows to blit nothing (or to blit one pixel on top of itself), or alternately you could intercept WM_WINDOWPOSCHANGING (first passing it onto DefWindowProc) and set WINDOWPOS.flags |= SWP_NOCOPYBITS, which disables the BitBlt inside the internal call to SetWindowPos() that Windows makes during window resizing. This has the same eventual effect of skipping the BitBlt.
However, nothing can be so simple. With the advent of Windows 8/10 Aero, apps now draw into an offscreen buffer which is then composited by the new, evil DWM.exe window manager. And it turns out DWM.exe will sometimes do its own BitBlt type operation on top of the one already done by the legacy XP/Vista/7 code. And stopping DWM from doing its blit is much harder; so far I have not seen any complete solutions.
So you need to get through both layers. For sample code that will break through the XP/Vista/7 layer and at least improve the performance of the 8/10 layer, see:
How to smooth ugly jitter/flicker/jumping when resizing windows, especially dragging left/top border (Win 7-10; bg, bitblt and DWM)?

Answer 2

What if you have a borderless childwindow (the type that only renders inside the parent) at a fixed size (same as fullscreen resolution), you should get a lot smoother results because there is no memory reallocation (which i think is what causes the jitterieness).
If it's still not perfect, look into both WM_SIZE and WM_SIZING and check if you can do some magic with them. For instance, on WM_SIZING you could return true telling Windows you handled the message (leaving the window as is) and you re-render your UI to a buffer with the size provided by WM_SIZING and when that is done, you send your own WM_SIZING but with a manipulated unused bit in WPARAM (along with its previous content) that tells you you have a pre-rendered buffer for this that you can just blit out. From the WM_SIZING documentation on msdn it looks like WPARAM should have a couple of bits at your disposal.
Hope this helps.

Answer 3

When calling CreateSwapChainForHwnd, ensure that you have set the swap chain description Scaling property to DXGI_SCALING_NONE. This is only supported on Windows 7 with the Platform Update, so you may need to fall back to the default DXGI_SCALING_STRETCH (the latter is what is causing the flickering).

Answer 4

Set WM_SETREDRAW to FALSE, do your resizing, then reenable drawing, invalidate the window and the OS will blit it.
I've done this for button enabling and disabling buttons when selecting different items from a list, never for an entire window.

Answer 5

This is the best I've come up with and resizes great although the backbuffer blitting causes some edge flickering, haven't tested with DX or OGL yet but it should work even better with hardware acceleration. It's a bit bulky but will do as a proof of concept.
If the canvas could be clipped without using MDI that would be even better, like using a bitmask buffer.
One thing i'm not happy about is the position coords of the child window because they might not work on all systems, but a combination of GetSystemMetrics calls to get border and caption sizes should fix that.
/* Smooth resizing of GDI+ MDI window
*
* Click window to resize, hit Escape or Alt+F4 to quit
*
* Character type is set to multibyte
* Project->Properties->Config Properties->General->Character Set = Multibyte
*
* Pritam 2014 */
// Includes
#include <Windows.h>
#include <gdiplus.h>
#pragma comment (lib,"Gdiplus.lib")
using namespace Gdiplus;
// Max resolution
#define XRES 1600
#define YRES 900
// Globals
bool resizing = false;
HWND parent, child; // child is the canvas window, parent provides clipping of child
Bitmap * buffer;
// Render
void Render() {
// Get parent client size
RECT rc;
GetClientRect(parent, &rc);
// Draw backbuffer
Graphics * g = Graphics::FromImage(buffer);
// Clear buffer
g->Clear(Color(100, 100, 100));
// Gray border
Pen pen(Color(255, 180, 180, 180));
g->DrawRectangle(&pen, 10, 10, rc.right - 20, rc.bottom - 20);
pen.SetColor(Color(255, 0, 0, 0));
g->DrawRectangle(&pen, 0, 0, rc.right - 1, rc.bottom - 1);
// Draw buffer to screen
PAINTSTRUCT ps;
HDC hdc = BeginPaint(child, &ps);
Graphics graphics(hdc);
graphics.DrawImage(buffer, Point(0, 0));
// Free
EndPaint(child, &ps);
}
// MDI Callback
LRESULT CALLBACK MDICallback(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
switch(message) {
case WM_LBUTTONDOWN:
resizing = true; // Start resizing
return 0;
break;
case WM_KEYDOWN:
if(wparam == VK_ESCAPE) { // Exit on escape
PostQuitMessage(0);
}
TranslateMessage((const MSG *)&message);
return 0;
break;
case WM_PAINT:
Render();
return 0;
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
break;
}
return DefMDIChildProc(hwnd, message, wparam, lparam);
}
// Parent window callback
LRESULT CALLBACK WndCallback(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {
return DefFrameProc(hwnd, child, message, wparam, lparam);
}
// Create windows
bool CreateWindows(void) {
// Parent class
WNDCLASSEX wndclass;
ZeroMemory(&wndclass, sizeof(wndclass)); wndclass.cbSize = sizeof(wndclass);
wndclass.style = CS_NOCLOSE;
wndclass.lpfnWndProc = WndCallback;
wndclass.hInstance = GetModuleHandle(NULL);
wndclass.lpszClassName = "WNDCALLBACKPARENT";
wndclass.hIcon = LoadIcon(NULL, IDI_WINLOGO);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
if(!RegisterClassEx(&wndclass)) return false;
// MDI class
wndclass.style = CS_OWNDC | CS_VREDRAW | CS_HREDRAW;
wndclass.lpfnWndProc = MDICallback;
wndclass.lpszClassName = "MDICALLBACKCANVAS";
if(!RegisterClassEx(&wndclass)) return false;
// Parent window styles
DWORD style = WS_POPUP | WS_CLIPCHILDREN;
DWORD exstyle = 0;
// Set initial window size and position
RECT rc;
rc.right = 640;
rc.bottom = 480;
AdjustWindowRectEx(&rc, style, false, exstyle);
rc.left = 20;
rc.top = 20;
// Create window
if(!(parent = CreateWindowEx(exstyle, "MDICLIENT", "MDI Resize", style, rc.left, rc.top, rc.right, rc.bottom, NULL, NULL, wndclass.hInstance, NULL))) return false;
// MDI window styles
style = MDIS_ALLCHILDSTYLES;
exstyle = WS_EX_MDICHILD;
// Set MDI size
rc.left = - 8; // The sizes occupied by borders and caption, if position is not correctly set an ugly caption will appear
rc.top = - 30;
rc.right = XRES;
rc.bottom = YRES;
AdjustWindowRectEx(&rc, style, false, exstyle);
// Create MDI child window
if(!(child = CreateWindowEx(exstyle, "MDICALLBACKCANVAS", "", style, rc.left, rc.top, rc.right, rc.bottom, parent, NULL, wndclass.hInstance, NULL))) return 8;
// Finalize
ShowWindow(child, SW_SHOW);
ShowWindow(parent, SW_SHOWNORMAL);
// Success
return true;
}
// Resize
void Resize(void) {
// Init
RECT rc, rcmdi;
GetClientRect(child, &rcmdi); // Use mdi window size to set max resize for parent
GetWindowRect(parent, &rc);
// Get mouse position
POINT mp;
GetCursorPos(&mp);
// Set new size
rc.right = mp.x - rc.left + 10;
rc.bottom = mp.y - rc.top + 10;
// Apply min & max size
if(rc.right < 240) rc.right = 240; if(rc.bottom < 180) rc.bottom = 180;
if(rc.right > rcmdi.right) rc.right = rcmdi.right; if(rc.bottom > rcmdi.bottom) rc.bottom = rcmdi.bottom;
// Update window size
SetWindowPos(parent, NULL, rc.left, rc.top, rc.right, rc.bottom, SWP_NOZORDER | SWP_NOMOVE);
// Make sure client is entirely repainted
GetClientRect(child, &rc);
InvalidateRect(child, &rc, false);
UpdateWindow(child);
// Stop resizing if mousebutton is up
if(!(GetKeyState(VK_LBUTTON) & 1 << (sizeof(short) * 8 - 1)))
resizing = false;
}
// Main
int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE pinstance, LPSTR cmdline, int cmdshow) {
// Initiate GDI+
ULONG_PTR gdiplusToken;
GdiplusStartupInput gdiplusStartupInput;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
buffer = new Bitmap(XRES, YRES, PixelFormat24bppRGB);
// Create windows
if(!CreateWindows()) return 1;
// Main loop
bool running = true;
MSG message;
while(running) {
// Check message or pass them on to window callback
if(PeekMessage(&message, NULL, 0, 0, PM_REMOVE)) {
if(message.message == WM_QUIT) {
running = false;
} else {
if(!TranslateMDISysAccel(child, &message)) {
TranslateMessage(&message);
DispatchMessage(&message);
}
}
}
// Resize
if(resizing)
Resize();
// Sleep a millisecond to spare the CPU
Sleep(1);
}
// Free memmory and exit
delete buffer;
GdiplusShutdown(gdiplusToken);
return 0;
}
Edit: Another example using "bitmask"/layered window.
// Escape to quit, left mousebutton to move window, right mousebutton to resize.
// And again char set must be multibyte
// Include
#include <Windows.h>
#include <gdiplus.h>
#pragma comment (lib,"Gdiplus.lib")
using namespace Gdiplus;
// Globals
Bitmap * backbuffer;
int xres, yres;
bool move, size;
POINT framePos, frameSize, mouseOffset;
// Renders the backbuffer
void Render(void) {
if(!backbuffer) return;
// Clear window with mask color
Graphics * gfx = Graphics::FromImage(backbuffer);
gfx->Clear(Color(255, 0, 255));
// Draw stuff
SolidBrush brush(Color(120, 120, 120));
gfx->FillRectangle(&brush, framePos.x, framePos.y, frameSize.x, frameSize.y);
}
// Paints the backbuffer to window
void Paint(HWND hwnd) {
if(!hwnd) return;
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
Graphics gfx(hdc);
gfx.DrawImage(backbuffer, Point(0, 0));
EndPaint(hwnd, &ps);
}
void HandleMove(HWND hwnd) {
// Get mouse position
POINT mouse;
GetCursorPos(&mouse);
// Update frame position
framePos.x = mouse.x - mouseOffset.x;
framePos.y = mouse.y - mouseOffset.y;
// Redraw buffer and invalidate & update window
Render();
InvalidateRect(hwnd, NULL, false);
UpdateWindow(hwnd);
// Stop move
if(!(GetKeyState(VK_LBUTTON) & 1 << (sizeof(short) * 8 - 1)))
move = false;
}
void HandleSize(HWND hwnd) {
// Get mouse position
POINT mouse;
GetCursorPos(&mouse);
// Update frame size
frameSize.x = mouse.x + mouseOffset.x - framePos.x;
frameSize.y = mouse.y + mouseOffset.y - framePos.y;
//frameSize.x = mouse.x + mouseOffset.x;
//frameSize.y = mouse.y + mouseOffset.y;
// Redraw buffer and invalidate & update window
Render();
InvalidateRect(hwnd, NULL, false);
UpdateWindow(hwnd);
// Stop size
if(!(GetKeyState(VK_RBUTTON) & 1 << (sizeof(short) * 8 - 1)))
size = false;
}
LRESULT CALLBACK WindowCallback(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam) {
POINTS p;
switch(msg) {
case WM_KEYDOWN:
if(wparam == VK_ESCAPE) PostQuitMessage(0);
return 0;
break;
case WM_LBUTTONDOWN:
p = MAKEPOINTS(lparam); // Get mouse coords
mouseOffset.x = p.x - framePos.x;
mouseOffset.y = p.y - framePos.y;
move = true;
break;
case WM_RBUTTONDOWN:
p = MAKEPOINTS(lparam);
mouseOffset.x = framePos.x + frameSize.x - p.x;
mouseOffset.y = framePos.y + frameSize.y - p.y;
size = true;
break;
case WM_PAINT:
Paint(hwnd);
return 0;
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
break;
}
return DefWindowProc(hwnd, msg, wparam, lparam);
}
// Main
int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE pinstance, LPSTR cmdline, int cmdshow) {
// Init resolution, frame
xres = GetSystemMetrics(SM_CXSCREEN);
yres = GetSystemMetrics(SM_CYSCREEN);
move = false; size = false;
framePos.x = 100; framePos.y = 80;
frameSize.x = 320; frameSize.y = 240;
mouseOffset.x = 0; mouseOffset.y = 0;
// Initiate GDI+
ULONG_PTR gdiplusToken;
GdiplusStartupInput gdiplusStartupInput;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
// Init backbuffer
backbuffer = ::new Bitmap(xres, yres, PixelFormat24bppRGB);
Render();
// Window class
WNDCLASSEX wc; ZeroMemory(&wc, sizeof(wc)); wc.cbSize = sizeof(wc);
wc.style = CS_OWNDC | CS_VREDRAW | CS_HREDRAW;
wc.lpfnWndProc = WindowCallback;
wc.hInstance = GetModuleHandle(NULL);
wc.lpszClassName = "SingleResizeCLASS";
wc.hIcon = LoadIcon(NULL, IDI_WINLOGO);
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
if(!RegisterClassEx(&wc)) return 1;
// Create window
HWND hwnd;
DWORD style = WS_POPUP;
DWORD exstyle = WS_EX_LAYERED;
if(!(hwnd = CreateWindowEx(exstyle, wc.lpszClassName, "Resize", style, 0, 0, xres, yres, NULL, NULL, wc.hInstance, NULL)))
return 2;
// Make window fully transparent to avoid the display of unpainted window
SetLayeredWindowAttributes(hwnd, 0, 0, LWA_ALPHA);
// Finalize
ShowWindow(hwnd, SW_SHOWNORMAL);
UpdateWindow(hwnd);
// Make window fully opaque, and set color mask key
SetLayeredWindowAttributes(hwnd, RGB(255, 0, 255), 0, LWA_COLORKEY);
// Main loop
MSG msg;
bool running = true;
while(running) {
// Check message
if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
if(msg.message == WM_QUIT) {
running = false;
} else {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
// Move or size frame
if(move) { HandleMove(hwnd); }
if(size) { HandleSize(hwnd); }
Sleep(1);
}
// Free memory
::delete backbuffer;
backbuffer = NULL;
GdiplusShutdown(gdiplusToken);
// Exit
return 0;
}

Answer 6

While your aim is laudable, I suspect that any attempt to do this will just end up as a fight between you and Windows - which you will not win (though you might manage to fight your way to an honourable draw). Sorry to be negative.