Link SCROLLINFO to my scrollbar — WINAPI C++ - c++

Question

I have a window with a working default scrollbar.
Now I'd like to link all the code I have to the custom scrollbar created via CreateWindow
Here is the procedure that
LRESULT CALLBACK InfoProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam, UINT_PTR, DWORD_PTR) {
switch (msg) {
case WM_COMMAND:
if(wParam == ID_CLOSECROSS){
if(IsWindowVisible(aboutPanel)) SwitchToWindow(aboutPanel); else SwitchToWindow(howToPanel);
}
break;
case WM_MOUSEWHEEL:{
if((short)HIWORD(wParam) > 0){
SendMessage(hwnd, WM_VSCROLL, VK_UP, 0);
}else{
SendMessage(hwnd, WM_VSCROLL, VK_DOWN, 0);
}
break;
}
case WM_VSCROLL:{
RECT hrc; GetClientRect(hwnd, &hrc);
SCROLLINFO si;
si.cbSize = sizeof (si);
si.fMask = SIF_ALL;
GetScrollInfo (hwnd, SB_VERT, &si);
int pos;
yPos = si.nPos;
switch (LOWORD (wParam)){
case SB_TOP: si.nPos = si.nMin; break;
case SB_BOTTOM: si.nPos = si.nMax; break;
case SB_LINEUP: si.nPos -= 1; break;
case SB_LINEDOWN: si.nPos += 1; break;
case VK_UP: si.nPos -= 20; break;
case VK_DOWN: si.nPos += 20; break;
case SB_PAGEUP: si.nPos -= si.nPage; break;
case SB_PAGEDOWN: si.nPos += si.nPage; break;
case SB_THUMBTRACK: si.nPos = si.nTrackPos; pos = HIWORD(wParam); break;
}
si.fMask = SIF_POS;
SetScrollInfo (hwnd, SB_VERT, &si, TRUE);
GetScrollInfo (hwnd, SB_VERT, &si);
if (si.nPos != yPos){
ScrollWindow(centerHowToPanel, 0, scrollSpeed*(yPos-si.nPos), NULL, &hrc);
// here
UpdateWindow (centerHowToPanel);
}
return 0;
}
case WM_SIZE:{
RECT hrc = { 0 };
GetClientRect(hwnd, &hrc);
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_ALL;
si.nMin = 0;
si.nMax = 30 * 99 + 21;
si.nPage = (hrc.bottom - hrc.top);
si.nPos = yPos;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, true);
// here
}
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
Here is my scrollbar I create in WinMain:
howToScroll = CreateWindow(L"SCROLLBAR", NULL, WS_VISIBLE|WS_CHILD|SBS_VERT, 0, 0, 0, 0, howToPanel, NULL, NULL, NULL);
If I replace each (Get|Set)ScrollInfo(hwnd, ...) with (Get|Set)ScrollInfo(howToScroll, ...) in the procedure it almost works. I can use scrollbar's arrows, but can't drag it. Also mouse wheel doesn't seem to change custom scrollbar's position.
I tried to use SetScrollPos(howToScroll, SB_CTL, yPos, 1); in the procedure at places where is commented 'here' word but it doesn't help either.
Also when resizing my custom scrollbar doesn't change it's size as default one does.
Just a quick demostration how it works with the default scrollbar.
                                                             
And here how it works with the custom one.
                                                             
Edit 1
I managed to make it scroll!
LRESULT CALLBACK InfoProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam, UINT_PTR, DWORD_PTR) {
switch (msg) {
case WM_COMMAND:
if(wParam == ID_CLOSECROSS){
if(IsWindowVisible(aboutPanel)) SwitchToWindow(aboutPanel); else SwitchToWindow(howToPanel);
}
break;
case WM_MOUSEWHEEL:{
if((short)HIWORD(wParam) > 0){
SendMessage(hwnd, WM_VSCROLL, VK_UP, 0);
}else{
SendMessage(hwnd, WM_VSCROLL, VK_DOWN, 0);
}
break;
}
case WM_VSCROLL:{
RECT hrc; GetClientRect(hwnd, &hrc);
SCROLLINFO si;
si.cbSize = sizeof (si);
si.fMask = SIF_ALL;
GetScrollInfo (howToScroll, SB_VERT, &si);
int pos;
yPos = si.nPos;
switch (LOWORD (wParam)){
case SB_TOP: si.nPos = si.nMin; break;
case SB_BOTTOM: si.nPos = si.nMax; break;
case SB_LINEUP: si.nPos -= 1; break;
case SB_LINEDOWN: si.nPos += 1; break;
case VK_UP: si.nPos -= 20; break;
case VK_DOWN: si.nPos += 20; break;
case SB_PAGEUP: si.nPos -= si.nPage; break;
case SB_PAGEDOWN: si.nPos += si.nPage; break;
case SB_THUMBTRACK: si.nPos = HIWORD(wParam); break;
}
SetScrollPos(howToScroll, SB_CTL, yPos, true);
si.fMask = SIF_POS;
SetScrollInfo (howToScroll, SB_VERT, &si, TRUE);
GetScrollInfo (howToScroll, SB_VERT, &si);
if (si.nPos != yPos){
ScrollWindow(centerHowToPanel, 0, scrollSpeed*(yPos-si.nPos), NULL, &hrc);
UpdateWindow (centerHowToPanel);
}
return 0;
}
case WM_SIZE:{
RECT hrc = { 0 };
GetClientRect(hwnd, &hrc);
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_ALL;
si.nMin = 0;
si.nMax = hrc.bottom+40;
SetScrollRange(howToScroll, SB_CTL, 0, hrc.bottom+40, TRUE);
si.nPage = (hrc.bottom - hrc.top);
si.nPos = yPos;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, true);
}
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
Now it seems like the head of the scroll is not big enough so it doesn't goes to the end of the bar.
                                                             
The only thing I need to manage -- the size of the scroll.
Edit 2
If I replace every single SB_VERT with SB_CTL it works as should! Thanks #JonathanPotter for that.