How to draw over second monitor with GDIPLUS

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I'm want to draw some text and lines over the desktop.

I'm using gdiplus.h for print texts with the function DrawString.

But its only print text on a primary screen monitor.

If has in presentation mode, with 2 monitors I need to print text in a second monitor.

C++

#define _WIN32_WINNT 0x500
#include <windows.h>
#include <gdiplus.h>

using namespace Gdiplus;

#pragma comment (lib,"Gdiplus.lib")

int main() {

    HWND desktop = GetDesktopWindow();
    HDC hdc = GetWindowDC(desktop); 

    ULONG_PTR m_gdiplusToken;
    // Initialize GDI+
    GdiplusStartupInput gdiplusStartupInput;
    GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);

    while (true)
    {

        HPEN newpen;
        LPPOINT point = NULL;
        newpen = CreatePen(PS_COSMETIC, 20, RGB(255, 0, 0));
        SelectObject(hdc, newpen);
        MoveToEx(hdc, 1500, 500, point);
        LineTo(hdc, 1600, 550 ); 
        //this block works for draw line in second monitor

        TextOut(hdc, 1500, 300, TEXT("Text of text out"), 17); // this works too


    //But if I'm use gdiplus only print things on the primary screen
    Gdiplus::Graphics g(hdc);

    Pen      pen(Gdiplus::Color(0, 0, 255), 2);

    g.DrawLine(&pen, 1500, 0, 1700, 600);// dont work

    g.DrawLine(&pen, 0, 0, 1200, 600);//  work, but is in the primary screen

    FontFamily  fontFamily(L"Times New Roman");
    Font        font(&fontFamily, 24, FontStyleRegular, UnitPixel);
    SolidBrush  brush(Color(255, 0, 0, 255));

    g.DrawString(TEXT("test of GDI+"), 13, &font, PointF(1600.0f, 300.0f), &brush); // dont work

    g.DrawString(TEXT("test of GDI+"), 13, &font, PointF(500.0f, 300.0f), &brush); // work, but is in the primary screen
    }

    Gdiplus::GdiplusShutdown(m_gdiplusToken);

    return 0;
}

Posted 24-Mar-15 12:05pm

Paulo Filipe Dantas

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barneyman · Answer 1 · 2015-03-24T14:17:00

Solution 1

this (Device Contexts on Multiple Monitors)[^] might be useful

Posted 24-Mar-15 14:17pm

barneyman

Comments

Paulo Filipe Dantas 25-Mar-15 1:40am

@barneyman
Thanks for help.
I'm try with this, HDC hdc = GetDC(NULL); , that documentation say get the virtual screen. But doesnt work too.

if I'm change
"
HWND desktop = GetDesktopWindow();
HDC hdc = GetWindowDC(desktop);
"
for
"
HDC hdc = GetDC(NULL);
"
the result of the code above is the same.

You can help-me showing the code to draw on the second monitor??

barneyman 25-Mar-15 6:58am

did you look at that link? it explains that all DCs you get are normally for the primary monitor - it suggests using EnumDisplayMonitors/GetMonitorInfo/CreateDC

Paulo Filipe Dantas 25-Mar-15 13:46pm

@barneyman
Yes, I'm tryied with this way

#include <iostream>
#define _WIN32_WINNT 0x500
#include <windows.h>
#include <gdiplus.h>

using namespace Gdiplus;

#pragma comment (lib,"Gdiplus.lib")

HDC hdc;

BOOL CALLBACK MonitorEnumProcCallback(_In_ HMONITOR hMonitor, _In_ HDC DevC, _In_ LPRECT lprcMonitor, _In_ LPARAM dwData) {

MONITORINFOEX info;
info.cbSize = sizeof(MONITORINFO);

BOOL monitorInfo = GetMonitorInfo(hMonitor, &info);

cout << "info szDevice" << info.szDevice << endl;

if (monitorInfo) {
hdc = CreateDC(NULL, info.szDevice, NULL, NULL);
}

return TRUE;
}

int main() {

HWND desktop = GetDesktopWindow();
HDC DevC = GetDC(desktop);
BOOL b = EnumDisplayMonitors(DevC, NULL, MonitorEnumProcCallback, 0);

ULONG_PTR m_gdiplusToken;
// Initialize GDI+
GdiplusStartupInput gdiplusStartupInput;
GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);

while (true)
{
HPEN newpen;
LPPOINT point = NULL;
newpen = CreatePen(PS_COSMETIC, 20, RGB(255, 0, 0));
SelectObject(hdc, newpen);
MoveToEx(hdc, 1500, 500, point);
LineTo(hdc, 1600, 550);
//this block works for draw line in second monitor

TextOut(hdc, 1500, 300, TEXT("Text of text out"), 17); // this works too

//But if I'm use gdiplus only print things on the primary screen
Gdiplus::Graphics g(hdc);

Pen pen(Gdiplus::Color(0, 0, 255), 2);

g.DrawLine(&pen, 1500, 0, 1700, 600);// dont work

g.DrawLine(&pen, 0, 0, 1200, 600);// work, but is in the primary screen

FontFamily fontFamily(L"Times New Roman");
Font font(&fontFamily, 24, FontStyleRegular, UnitPixel);
SolidBrush brush(Color(255, 0, 0, 255));

g.DrawString(TEXT("test of GDI+"), 13, &font, PointF(1600.0f, 300.0f), &brush); // dont work

g.DrawString(TEXT("test of GDI+"), 13, &font, PointF(500.0f, 300.0f), &brush); // work, but is in the primary screen
}

Gdiplus::GdiplusShutdown(m_gdiplusToken);

return 0;
}

and I'm tryied too with

BOOL b = EnumDisplayMonitors(NULL, NULL, MonitorEnumProcCallback, 0);

and dosent work for any case, dont print anything in the any monitors

barneyman 25-Mar-15 17:20pm

sorry - no idea - a quick google, and you're not the first to find that problem with GDI+

Paulo Filipe Dantas 25-Mar-15 18:17pm

Yes, I'm put this question in other places.