Version:           KWin 3.0 (using KDE KDE 3.4.2)
Installed from:    Slackware Packages
OS:                Linux

Please, run the attached test case.

1. You will see the simple window.
2. Try to maximize this window.
BUT no maximize button available.

In this test I'm using XSetWMNormalHints / PMaxSize in order to specify maximum size.
This leads to removing _NET_WM_ACTION_MAXIMIZE_XXX from _NET_WM_ALLOWED_ACTIONS.

This behaviour is different from others window managers (metacity / wmaker).

SOURCE CODE
===============================
// gcc test.c -L /usr/X11R6/lib -l X11

#include<X11/Xlib.h>
#include<X11/Xutil.h>
#include<stdio.h>
#define BORDER_WIDTH 2


/* Program wide globals */
Display *theDisplay;
int theScreen;
int theDepth;

Window OpenWindow(int x, int y, int width, int height, int flag){
        XSetWindowAttributes theWindowAttributes;
        unsigned long theWindowMask;
        XSizeHints theSizeHints;
        XWMHints theWMHints;
        Window theNewWindow;

        /*Setting the attributes*/
        theWindowAttributes.border_pixel
                =BlackPixel(theDisplay,theScreen);
        theWindowAttributes.background_pixel
                = WhitePixel(theDisplay,theScreen);
        theWindowAttributes.override_redirect = False;

        theWindowMask = CWBackPixel|CWBorderPixel|CWOverrideRedirect;

        theNewWindow = XCreateWindow( theDisplay,
                        RootWindow(theDisplay,theScreen),
                        x,y,width,height,
                        BORDER_WIDTH,theDepth,
                        InputOutput,
                        CopyFromParent,
                        theWindowMask,
                        &theWindowAttributes);


        theWMHints.initial_state = NormalState;
        theWMHints.flags = StateHint;


        XSetWMHints(theDisplay,theNewWindow,&theWMHints);

	// PMaxSize doesn't work
	theSizeHints.flags = PPosition | PSize | PMaxSize | PResizeInc;
        theSizeHints.x = x;
        theSizeHints.y = y;
        theSizeHints.width = width;
        theSizeHints.height = height;
	theSizeHints.max_width = 200;
	theSizeHints.max_height = 200;
	theSizeHints.width_inc = 10;
	theSizeHints.height_inc = 10;

        XSetWMNormalHints(theDisplay,theNewWindow,&theSizeHints);

        XMapWindow(theDisplay,theNewWindow);
        XFlush(theDisplay);


        return theNewWindow;
}


int main(void){
        Window theWindow;

        theDisplay = XOpenDisplay(NULL);

        theScreen = DefaultScreen(theDisplay);
        theDepth = DefaultDepth(theDisplay,theScreen);

        theWindow = OpenWindow(50,50,100,100,0);
        XFlush(theDisplay);

        sleep(100);
        XDestroyWindow(theDisplay,theWindow);
}