glfw/src/win32/win32_fullscreen.c

//========================================================================
// GLFW - An OpenGL framework
// Platform:    Win32/WGL
// API version: 3.0
// WWW:         http://www.glfw.org/
//------------------------------------------------------------------------
// Copyright (c) 2002-2006 Marcus Geelnard
// Copyright (c) 2006-2010 Camilla Berglund <elmindreda@elmindreda.org>
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgment in the product documentation would
//    be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
//    be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
//    distribution.
//
//========================================================================

#include "internal.h"


//========================================================================
// Convert BPP to RGB bits based on "best guess"
//========================================================================

static void bpp2rgb(int bpp, int* r, int* g, int* b)
{
    int delta;

    // We assume that by 32 they really meant 24
    if (bpp == 32)
        bpp = 24;

    // Convert "bits per pixel" to red, green & blue sizes

    *r = *g = *b = bpp / 3;
    delta = bpp - (*r * 3);
    if (delta >= 1)
        *g = *g + 1;

    if (delta == 2)
        *r = *r + 1;
}


//========================================================================
// Return closest video mode by dimensions, refresh rate and channel sizes
//========================================================================

static int getClosestVideoMode(int* w, int* h,
                               int* r, int* g, int* b,
                               int* refresh)
{
    int bpp, bestmode;

    // Colorbits = sum of red/green/blue bits
    bpp = *r + *g + *b;

    // If colorbits < 15 (e.g. 0) or >= 24, default to 32 bpp
    if (bpp < 15 || bpp >= 24)
        bpp = 32;

    // Find best match
    bestmode = _glfwGetClosestVideoModeBPP(w, h, &bpp, refresh);

    // Convert "bits per pixel" to red, green & blue sizes
    bpp2rgb(bpp, r, g, b);

    return bestmode;
}


//////////////////////////////////////////////////////////////////////////
//////                       GLFW internal API                      //////
//////////////////////////////////////////////////////////////////////////

//========================================================================
// Return closest video mode by dimensions, refresh rate and bits per pixel
//========================================================================

int _glfwGetClosestVideoModeBPP(int* w, int* h, int* bpp, int* refresh)
{
    int mode, bestmode, match, bestmatch, rr, bestrr, success;
    DEVMODE dm;

    // Find best match
    bestmatch = 0x7fffffff;
    bestrr    = 0x7fffffff;
    mode = bestmode = 0;

    do
    {
        dm.dmSize = sizeof(DEVMODE);
        success = EnumDisplaySettings(NULL, mode, &dm);
        if (success)
        {
            match = dm.dmBitsPerPel - *bpp;
            if (match < 0)
                match = -match;

            match = (match << 25) |
                    ((dm.dmPelsWidth - *w) *
                     (dm.dmPelsWidth - *w) +
                     (dm.dmPelsHeight - *h) *
                     (dm.dmPelsHeight - *h));
            if (match < bestmatch)
            {
                bestmatch = match;
                bestmode  = mode;
                bestrr = (dm.dmDisplayFrequency - *refresh) *
                         (dm.dmDisplayFrequency - *refresh);
            }
            else if (match == bestmatch && *refresh > 0)
            {
                rr = (dm.dmDisplayFrequency - *refresh) *
                     (dm.dmDisplayFrequency - *refresh);
                if (rr < bestrr)
                {
                    bestmatch = match;
                    bestmode  = mode;
                    bestrr    = rr;
                }
            }
        }
        mode++;
    }
    while (success);

    // Get the parameters for the best matching display mode
    dm.dmSize = sizeof(DEVMODE);
    EnumDisplaySettings(NULL, bestmode, &dm);

    // Fill out actual width and height
    *w = dm.dmPelsWidth;
    *h = dm.dmPelsHeight;

    // Return bits per pixel
    *bpp = dm.dmBitsPerPel;

    // Return vertical refresh rate
    *refresh = dm.dmDisplayFrequency;

    return bestmode;
}


//========================================================================
// Change the current video mode
//========================================================================

void _glfwSetVideoModeMODE(int mode)
{
    DEVMODE dm;
    int success;

    // Get the parameters for the best matching display mode
    dm.dmSize = sizeof(DEVMODE);
    EnumDisplaySettings(NULL, mode, &dm);

    // Set which fields we want to specify
    dm.dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_BITSPERPEL;

    // Do we have a prefered refresh rate?
    if (_glfwWin.desiredRefreshRate > 0)
    {
        dm.dmFields = dm.dmFields | DM_DISPLAYFREQUENCY;
        dm.dmDisplayFrequency = _glfwWin.desiredRefreshRate;
    }

    // Change display setting
    dm.dmSize = sizeof(DEVMODE);
    success = ChangeDisplaySettings(&dm, CDS_FULLSCREEN);

    // If the mode change was not possible, query the current display
    // settings (we'll use the desktop resolution for fullscreen mode)
    if (success == DISP_CHANGE_SUCCESSFUL)
        _glfwWin.modeID = mode;
    else
    {
        _glfwWin.modeID = ENUM_REGISTRY_SETTINGS;
        EnumDisplaySettings(NULL, ENUM_REGISTRY_SETTINGS, &dm);
    }

    // Set the window size to that of the display mode
    _glfwWin.width  = dm.dmPelsWidth;
    _glfwWin.height = dm.dmPelsHeight;
}


//========================================================================
// Change the current video mode
//========================================================================

void _glfwSetVideoMode(int* w, int* h, int r, int g, int b, int refresh)
{
    int bestmode;

    // Find a best match mode
    bestmode = getClosestVideoMode(w, h, &r, &g, &b, &refresh);

    // Change mode
    _glfwSetVideoModeMODE(bestmode);
}


//////////////////////////////////////////////////////////////////////////
//////                       GLFW platform API                      //////
//////////////////////////////////////////////////////////////////////////

//========================================================================
// Get a list of available video modes
//========================================================================

int _glfwPlatformGetVideoModes(GLFWvidmode* list, int maxcount)
{
    int count, success, mode, i, j;
    int m1, m2, bpp, r, g, b;
    DEVMODE dm;

    // Loop through all video modes and extract all the UNIQUE modes
    count = 0;
    mode  = 0;

    do
    {
        // Get video mode properties
        dm.dmSize = sizeof(DEVMODE);
        success = EnumDisplaySettings(NULL, mode, &dm);

        // Is it a valid mode? (only list depths >= 15 bpp)
        if (success && dm.dmBitsPerPel >= 15)
        {
            // Convert to RGB, and back to bpp ("mask out" alpha bits etc)
            bpp2rgb(dm.dmBitsPerPel, &r, &g, &b);
            bpp = r + g + b;

            // Mode "code" for this mode
            m1 = (bpp << 25) | (dm.dmPelsWidth * dm.dmPelsHeight);

            // Insert mode in list (sorted), and avoid duplicates
            for (i = 0;  i < count;  i++)
            {
                // Mode "code" for already listed mode
                bpp = list[i].redBits + list[i].greenBits + list[i].blueBits;
                m2 = (bpp << 25) | (list[i].width * list[i].height);
                if (m1 <= m2)
                    break;
            }

            // New entry at the end of the list?
            if (i >= count)
            {
                list[count].width     = dm.dmPelsWidth;
                list[count].height    = dm.dmPelsHeight;
                list[count].redBits   = r;
                list[count].greenBits = g;
                list[count].blueBits  = b;
                count ++;
            }
            // Insert new entry in the list?
            else if (m1 < m2)
            {
                for (j = count;  j > i;  j--)
                    list[j] = list[j - 1];

                list[i].width     = dm.dmPelsWidth;
                list[i].height    = dm.dmPelsHeight;
                list[i].redBits   = r;
                list[i].greenBits = g;
                list[i].blueBits  = b;
                count++;
            }
        }
        mode++;
    }
    while (success && (count < maxcount));

    return count;
}


//========================================================================
// Get the desktop video mode
//========================================================================

void _glfwPlatformGetDesktopMode(GLFWvidmode* mode)
{
    DEVMODE dm;

    // Get desktop display mode
    dm.dmSize = sizeof(DEVMODE);
    EnumDisplaySettings(NULL, ENUM_REGISTRY_SETTINGS, &dm);

    // Return desktop mode parameters
    mode->width  = dm.dmPelsWidth;
    mode->height = dm.dmPelsHeight;
    bpp2rgb(dm.dmBitsPerPel, &mode->redBits, &mode->greenBits, &mode->blueBits);
}