dtwm: basic multihead(xinerama only) support

* maximization (also partially fixes strange Firefox behaviour)
* sane initial window placement

Firefox is stranger than most; it appears to maximize to double
X Screen width even on single head displays.  Fixed (on multihead).

cde/programs/dtwm/WmMultiHead.c

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2016 Matthew R. Trower
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+ * Included Files:
+ */
+#include <DtXinerama.h>
+
+#include "WmMultiHead.h"
+
+/*
+ * Global Variables
+ */
+DtXineramaInfo_t *DtXI = NULL;/* Xinerama data is static for life of X server */
+
+
+/*************************************<->*************************************
+ *
+ *  GetHeadInfo (pcd)
+ *
+ *
+ *  Description:
+ *  -----------
+ *  Search for the head containing target client.
+ *
+ *
+ *  Inputs:
+ *  ------
+ *
+ *
+ *  Outputs:
+ *  -------
+ *  Return = head metrics on success, NULL on failure.
+ *           menuWidget, and menuButtons members.
+ *
+ *
+ *  Comments:
+ *  --------
+ *
+ *  Can fail if:
+ *
+ *  - MultiHead(eg. Xinerama) is not active
+ *  - Client does not fall within any existing head
+ *  - malloc error
+ *  - pcd is NULL
+ *
+ *************************************<->***********************************/
+WmHeadInfo_t *GetHeadInfo(const ClientData *pcd) {
+    WmHeadInfo_t *WmHI = NULL;
+
+    if (!DtXI)
+        DtXI = _DtXineramaInit(DISPLAY);
+
+    if (!pcd || !DtXI)
+        return NULL;
+
+    if (!(WmHI = (WmHeadInfo_t *)malloc(sizeof(WmHeadInfo_t)))) {
+#ifdef DEBUG
+        fprintf(stderr, "(dtwm) _GetScreenInfo: malloc failed\n");
+#endif
+
+        free(DtXI);
+        return NULL;
+    }
+
+    /*
+     * TODO
+     *
+     * DtXineramaInfo_t uses unsigned ints
+     * XineramaScreenInfo uses shorts(?)
+     * ClientData uses ints
+     * FrameToClient and friends use a mixture (!)
+     *
+     * Explicit casting would shut the compiler up, but wouldn't change the
+     * fundamental fact that we can't agree on coordinate types.
+     */
+    int idx = 0;
+    while (_DtXineramaGetScreen(DtXI, idx++,
+            &WmHI->width, &WmHI->height, &WmHI->x_org, &WmHI->y_org)) {
+
+        if (pcd->clientX >= WmHI->x_org &&
+            pcd->clientY >= WmHI->y_org &&
+            pcd->clientX <= WmHI->x_org + WmHI->width &&
+            pcd->clientY <= WmHI->y_org + WmHI->height)
+
+            return WmHI;
+    }
+
+    /* No valid screen */
+    return NULL;
+}