Oxygen

I am working on a simple little library that helps me write Windows applications in plain C. It implements the object oriented paradigm, featuring single inheritance and virtual methods. The API is modeled loosely along the Python C API.

Hello World!

This is how the all time classic would be implemented:

#include "Oxygen.h"

int APIENTRY wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPTSTR lpCmdLine, _In_ int nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    Oxygen_Init("Hello");

    OxRect rc = { .iLeft = 40, .iTop = 30, .iWidth = 320, .iHeight = 240 };
    OxApp->oxWindow = OxWindow_New(NULL, &rc, "Powered by Oxygen");

    rc = (OxRect){ .iLeft = 20, .iTop = OxWIDGET_CENTER, .iWidth = -20, .iHeight = 20 };
    OxLabelObject* oxLabel = OxLabel_New(OxApp->oxWindow, &rc, "Hello World!");
    OxLabel_Align(oxLabel, OxALIGN_HORIZ_CENTER);

    OxWidget_ShowV(OxApp->oxWindow, TRUE);
    return OxApplication_Run();
}

The same code compiles on the GTK version (and generates a native app!)

An example of a more complex application would look like this:

#include "Oxygen.h"

typedef struct _ClientWindow {
    OxTabObject* oxTab;
    OxTabPageObject* oxTabPageDivision;
    OxEntryObject* oxEntryDividend;
    OxEntryObject* oxEntryDivisor;
    OxLabelObject* oxLabelQuotient;
    OxButtonObject* oxButtonDivide;
    OxTabPageObject* oxTabPageMultiplication;
    OxLabelObject* oxLabelMultiplication;
} ClientWindow;

// forward declarations
static BOOL WindowBeforeDeleteCB(OxWindowObject* ox);
static BOOL ButtonDivideCB(OxButtonObject* ox);
static BOOL DivisorVerifyCB(OxEntryObject* ox);
static void AboutCB();

int APIENTRY wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPTSTR lpCmdLine, _In_ int nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    OxCALL(Oxygen_Init("HOx")); // show error if result of call is FALSE

    OxRect rc = { .iLeft = 40, .iTop = 30, .iWidth = 600, .iHeight = 400 };
    OxASSIGN(OxApp->oxWindow = OxWindow_New(NULL, &rc, "Hello Oxygen")); // show error if assigned value is NULL
    OxApp->oxWindow->iMinHeight = 400;
    OxApp->sStateID = "HelloOxygen";
    OxCALL(OxApplication_RestoreState());

    OxMenuObject* oxMainMenu;
    OxASSIGN(oxMainMenu = OxMenu_New("Main Menu"));
    OxMenuObject* oxMdiWindowsMenu = OxMenu_New("Windows");
    OxMenuObject* oxHelpMenu = OxMenu_New("Help");
    OxMenuItemObject* oxMenuItem;
    OxIconObject* oxIcon = OxIcon_FromFile("Example.ico");
    OxASSIGN(oxMenuItem = OxMenuItem_New("About...", AboutCB, oxIcon));

    OxCALL(OxMenu_AppendItem(oxMainMenu, (OxObject*)oxMdiWindowsMenu));
    OxCALL(OxMenu_AppendItem(oxMainMenu, (OxObject*)oxHelpMenu));
    OxCALL(OxMenu_AppendItem(oxHelpMenu, (OxObject*)oxMenuItem));
    OxCALL(OxWindow_SetMenu(OxApp->oxWindow, oxMainMenu));

    OxToolBarObject* oxToolBar = OxToolBar_New((OxWidgetObject*)OxApp->oxWindow);
    //XX(oxToolBar);
    OxCALL(OxToolBar_AppendItem(oxToolBar, oxMenuItem));
    int iTB = OxToolBar_GetHeight(oxToolBar);

    int iParts[] = { 120, -50, 0 }; // three parts: separations at 120 from left, 50 from right, 0 as sentinel
    OxStatusBarObject* oxStatusBar = OxStatusBar_New((OxWidgetObject*)OxApp->oxWindow, iParts);
    OxStatusBar_Message(oxStatusBar, "Ready", 0);
    int iSB = OxStatusBar_GetHeight(oxStatusBar);

    rc = (OxRect){ .iLeft = 0, .iTop = iTB, .iWidth = 0, .iHeight = -iSB };
    OxMdiAreaObject* oxMdiArea = OxMdiArea_New((OxWidgetObject*)OxApp->oxWindow, &rc);
    OxMdiArea_SetMenu(oxMdiArea, oxMdiWindowsMenu);

    rc = (OxRect){ .iLeft = 10, .iTop = 10, .iWidth = 620, .iHeight = 440 };
    OxMdiWindowObject* oxMdiWindow = OxMdiWindow_New(oxMdiArea, &rc, "Calculator");
    oxMdiWindow->iMinHeight = 400;
    ClientWindow* pMW = (ClientWindow*)OxAllocate(sizeof(ClientWindow));
    oxMdiWindow->pUserData = pMW;
    OxWindowClass.aMethods[OxWIDGET_BEFOREDELETE] = WindowBeforeDeleteCB; // subclassing 'light'

    OxIconObject* oxExampleIcon = OxIcon_FromFile("Example.ico");

    rc = (OxRect){ .iLeft = 20, .iTop = 50, .iWidth = -20, .iHeight = -70 };
    OxASSIGN(pMW->oxTab = OxTab_New((OxWidgetObject*)oxMdiWindow, &rc));
    OxASSIGN(pMW->oxTabPageDivision = OxTabPage_New(pMW->oxTab, "Division", -1));


    rc = (OxRect){ .iLeft = 80, .iTop = 20, .iWidth = -20, .iHeight = 20 };
    OxASSIGN(pMW->oxEntryDividend = OxEntry_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc));
    pMW->oxEntryDividend->pDataType = &OxIntegerClass;
    rc.iLeft -= 60; rc.iWidth = 50;
    pMW->oxEntryDividend->oxLabel = OxLabel_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc, "Dividend");

    rc = (OxRect){ .iLeft = 80, .iTop = 50, .iWidth = -20, .iHeight = 20 };
    OxASSIGN(pMW->oxEntryDivisor = OxEntry_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc));
    pMW->oxEntryDivisor->fnVerifyCB = DivisorVerifyCB;
    pMW->oxEntryDivisor->pDataType = &OxIntegerClass;
    rc.iLeft -= 60; rc.iWidth = 50;
    pMW->oxEntryDividend->oxLabel = OxLabel_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc, "Divisor");

    rc = (OxRect){ .iLeft = 80, .iTop = 100, .iWidth = -20, .iHeight = 20 };
    OxASSIGN(pMW->oxLabelQuotient = OxLabel_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc));
    pMW->oxLabelQuotient->pDataType = &OxFloatClass;
    rc.iLeft -= 60; rc.iWidth = 50;
    pMW->oxLabelQuotient->oxLabel = OxLabel_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc, "Quotient");

    rc = (OxRect){ .iLeft = -110, .iTop = -40, .iWidth = 90, .iHeight = 20 };
    OxASSIGN(pMW->oxButtonDivide = OxButton_New((OxWidgetObject*)pMW->oxTabPageDivision, &rc, "Divide", ButtonDivideCB));

    OxASSIGN(pMW->oxTabPageMultiplication = OxTabPage_New(pMW->oxTab, "Multiplication", -1));

    rc = (OxRect){ .iLeft = 30, .iTop = OxWIDGET_CENTER, .iWidth = -30, .iHeight = 20 };
    pMW->oxLabelMultiplication = OxLabel_New((OxWidgetObject*)pMW->oxTabPageMultiplication, &rc, "Under Construction");
    OxLabel_Align(pMW->oxLabelMultiplication, OxALIGN_HORIZ_CENTER);

    return OxApplication_Run();
}

static BOOL
DivisorVerifyCB(OxEntryObject* ox)
{
    OxIntegerObject* oxDivisor = OxEntry_GetInputData(ox);
    if (oxDivisor && oxDivisor != OxNull && oxDivisor->iInteger == 0) {
        MessageBox(0, L"Division by zero not possible.", L"Error", MB_ICONERROR | MB_OK);
        return FALSE;
    }
    return TRUE;
}

static BOOL
ButtonDivideCB(OxButtonObject* ox)
{
    if (ox->oxWindow->oxFocusWidget) // validation callback not passed
        return TRUE;

    ClientWindow* pMW = (ClientWindow*)ox->oxWindow->pUserData;

    if (pMW->oxEntryDividend->oxData != OxNull && pMW->oxEntryDivisor->oxData != OxNull) {
        double dQuotient = ((OxIntegerObject*)pMW->oxEntryDividend->oxData)->iInteger / (double)((OxIntegerObject*)pMW->oxEntryDivisor->oxData)->iInteger;
        OxFloatObject* oxQuotient = OxFloat_New(dQuotient);

        OxCALL(OxLabel_SetData(pMW->oxLabelQuotient, oxQuotient));
    }
    else
        MessageBox(0, L"Division not possible.", L"Error", MB_ICONERROR | MB_OK);

    return TRUE;
}

static void
AboutCB()
{
    OxRect rc = { .iLeft = OxWIDGET_CENTER, .iTop = OxWIDGET_CENTER, .iWidth = 320, .iHeight = 240 };
    OxWindowObject* oxWindow = OxWindow_New(OxApp->oxWindow, &rc, "About Hello Oxygen");
    oxWindow->iMaxWidth = 320; oxWindow->iMaxHeight = 240;

    rc = (OxRect){ .iLeft = 40, .iTop = 40, .iWidth = -40, .iHeight = -40 };
    OxLabelObject* oxLabel = OxLabel_New((OxWidgetObject*)oxWindow, &rc, "Demonstration program for\nOxygen C library\n\nThomas Führinger, 2015");
    OxWindow_ShowModal(oxWindow);
    OxREL(oxLabel);
    OxREL(oxWindow);
    //return TRUE;
}

static BOOL
WindowBeforeDeleteCB(OxWindowObject* ox) // exit gracefully
{
    OutputDebugStringA(ox->pClass->sName);
    if (ox->pClass == &OxMdiWindowClass) {
        ClientWindow* pMW = (ClientWindow*)ox->pUserData;
        OxREL(pMW->oxLabelMultiplication);
        OxREL(pMW->oxTabPageMultiplication);
        OxREL(pMW->oxButtonDivide);
        OxREL(pMW->oxLabelQuotient);
        OxREL(pMW->oxEntryDividend);
        OxREL(pMW->oxEntryDivisor);
        OxREL(pMW->oxTabPageDivision);
        OxREL(pMW->oxTab);
        OxFree(pMW);
    }
    return TRUE;
}