Not drawing bitmap - c++

Question

GIF::GIF(Bitmap* bit, HDC hdc) {
this->bit = bit;
}
void GIF::draw(Graphics* g,HDC hdc, Bitmap *bit)
{
this->position.x = 50;
this->position.y = 50;
this->CachedBitmap = PNGLoader::createCachedBitmap(this->bit, hdc);
g->DrawCachedBitmap(CachedBitmap.get(), position.x, position.y);
}
std::shared_ptr<CachedBitmap> PNGLoader::createCachedBitmap(Bitmap*
originalBitmap, HDC hdc)
{
Graphics graphics(hdc);
return std::make_shared<CachedBitmap>(originalBitmap,
&graphics);
}
paint:
splash->draw(gt, hdc,new Bitmap(L"resoureses/Sample.gif"));
if I pass the value to this->bit when creating an instance of the class, and I pass it to the function and draw, then nothing works, and if I use a variable from GIF::Draw(Bitmap* bit), then everything works fine
init.
Main.h:
std::shared_ptr<CachedBitmap> CachedBitmap;
GIF* splash;
1st variant
void loadResources()
{
Bitmap* bitmap = new Bitmap(L"resoureses/Sample.gif");
splash = new GIF(bitmap, hdc);
}
void Paint(HDC hdc)
{
Graphics* gt = new Graphics(hdc);
splash->draw(gt, hdc);
}
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
Paint(hdc);
EndPaint(hwnd, &ps);
break;
}
WndProc(){
hwnd = CreateWindowExW(0, Wcc.lpszClassName, nullptr, WS_POPUP | WS_MINIMIZEBOX, x, y,
windowW, windowH, hWnd, NULL, (HINSTANCE)GetWindowLong(hParent, GWL_HINSTANCE), NULL);
loadResources(hwnd );
}
2nd variant
void loadResources()
{
Bitmap* bitmap = new Bitmap(L"resoureses/Sample.gif");
splash = new GIF(bitmap, hdc);
}
void Paint(HDC hdc)
{
Graphics* gt = new Graphics(hdc);
splash->draw(gt, hdc,new Bitmap(L"resoureses/Sample.gif"));
}
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hwnd, &ps);
Paint(hdc);
EndPaint(hwnd, &ps);
break;
}
WndProc(){
hwnd = CreateWindowExW(0, Wcc.lpszClassName, nullptr, WS_POPUP | WS_MINIMIZEBOX, x, y,
windowW, windowH, hWnd, NULL, (HINSTANCE)GetWindowLong(hParent, GWL_HINSTANCE), NULL);
loadResources(hwnd );
}

Answer 1

Looks like this line is causing the problem
this->CachedBitmap = PNGLoader::createCachedBitmap(this->bit, hdc);
This function GIF::draw is called repeatedly whenever windows have to be redrawn. So, when you assign a CachedBitmap first time with this->bit it should be ok. But as it is shared pointer, when you do it the second time, the stored CachedBitmap releases the pointer this->bit and it gets unusable before reassigning the shared_ptr newly returned by createCachedBitmap.
Instead, when you pass each time a new Bitmap before calling GIF::draw, you allocate new Bitmap so is no problem if you lose the old Bitmap
void GIF::draw(Graphics* g,HDC hdc, Bitmap *bit)
{
....
this->CachedBitmap = PNGLoader::createCachedBitmap(bit, hdc);
My suggestion is to assign this->CachedBitmap only once. For instance verify in GIF::draw if it is initialized, and if not assign, if yes do not assign. Or, do it outside draw function, in a place where you know it will be called only once.