rendering shapes and text on the desktop (click through)

Question

For Windows 7, what is the simplest way to render arbitrary shapes and text straight onto the desktop?

It must have the following properties:

1) Visible and always on top
3) Semi-transparent
2) Click through and type through, as if the objects are not there

Some notable examples range from the simple Fraps which renders framerate, to the complex Rainmeter which has tons of functionality.

EDIT0: I've looked at the Rainmeter sourcecode but I still have no idea how it renders objects...

EDIT1: Window Hud Behavior (Pass through clicks, can't be minimized) (Solutions such as this seem extremely restrictive, there must be a way to render stuff with as much freedom as Rainmeter?)

Answer 1

i am still working on it but here is part of it:

#include <algorithm>
#include <Windows.h>
#include <stdlib.h>
#include <iostream>
#include <sstream>
#include <conio.h>
#include <iomanip>
#include <sstream>
#include <fstream>
#include <stdio.h>
#include <cstdlib>
#include <string>
#include <memory>
#include <cstdio>            
#include <glut.h>
#include <io.h>

#using <mscorlib.dll>
#using <System.dll>

using namespace System;
using namespace std;

#pragma comment(lib, "wininet.lib")
#pragma comment (lib, "Urlmon.lib")
#pragma comment(linker, "/subsystem:windows /ENTRY:mainCRTStartup")

HINSTANCE hInstance;
POINT Mouse;
HWND hwnd;
RECT rect;
HDC dc;

float Size = 100;
float angle = 0;
bool Dirty = false;
char TEX;
int posX = 0;
int posY = 0;
int storedDC;

void GetDesktopResolution(int& w, int& h){
    RECT desktop;
    const HWND hDesktop = GetDesktopWindow();
    GetWindowRect(hDesktop, &desktop);
    w = desktop.right;
    h = desktop.bottom;
}

void EX(){
    delete hInstance;
    delete hwnd;
    exit(0);
}

void Keys(){
    if (GetAsyncKeyState(VK_ESCAPE)){
        exit(0);
    }

    if (GetAsyncKeyState(VK_LBUTTON) && GetAsyncKeyState(VK_CONTROL)){

    }
}

void Draw(){
    int h;
    int w;

    //Declair Desktop Size
    GetDesktopResolution(w, h);

    angle += 0.1f;

    if (angle >= 2 * 3.141592f){
        angle -= 2 * 3.141592f;
    }

    GetCursorPos(&Mouse);
    if (Dirty == true){
        rect = { 0, 0, w, h };
        RedrawWindow(hwnd, &rect, NULL, RDW_INVALIDATE | RDW_ERASE | RDW_UPDATENOW);

        posX = Mouse.x;
        posY = Mouse.y;

        RedrawWindow(hwnd, &rect, NULL, RDW_INVALIDATE | RDW_ERASE | RDW_UPDATENOW);
        Dirty = false;
    }

    dc = GetDC(hwnd);
    storedDC = SaveDC(dc);

    //DEFAULT_CHARSET - ANSI_CHARSET
    HFONT FMain = CreateFont(36, 20, -300, 0, FW_DONTCARE, FALSE, TRUE, FALSE, DEFAULT_CHARSET, OUT_OUTLINE_PRECIS,
        CLIP_DEFAULT_PRECIS, CLEARTYPE_QUALITY, VARIABLE_PITCH, TEXT("Times New Roman"));
    SetTextColor(dc, RGB(255, 255, 255));
    SetBkColor(dc, RGB(0, 255, 0));
    SelectObject(dc, FMain);
    TextOut(dc, 15, 15, L"This is what the program does!", 30);

    RedrawWindow(hwnd, &rect, NULL, RDW_NOERASE | RDW_INVALIDATE | RDW_UPDATENOW);

    RestoreDC(dc, storedDC);
    ReleaseDC(hwnd, dc);
}

int main(int argc, char **argv){
    int h;
    int w;

    //Declair Desktop Size
    GetDesktopResolution(w, h);

    // find Program Manager
    hwnd = FindWindowEx(GetDesktopWindow(), 0, L"Progman", L"Program Manager");
    // find SHELLDLL_DefView
    hwnd = FindWindowEx(hwnd, 0, L"SHELLDLL_DefView", 0);
    // find Desktop Folder
    hwnd = FindWindowEx(hwnd, 0, L"SysListView32", L"FolderView");

    if (hwnd == NULL){
        MessageBox(NULL, L"Could not initiate window!", L"ERROR!", MB_OK);
        EX();
    }

    while (1){
        Keys();
        Draw();
    }

    //Remove the drawing
    rect = { Mouse.x - 50, Mouse.y - 50, Mouse.x + 50, Mouse.y + 50 };
    InvalidateRect(hwnd, &rect, true);

    delete hInstance;
    delete hwnd;

    return 0;
}