Make initial scaling a float; prevent divide by zero

docs/labwc-config.5.scd

@@ -932,7 +932,7 @@ situation.
 *<magnifier><initScale>*
 	Initial number of times by which magnified image is scaled. Value
 	is the default at boot; can be modified at run-time in a keyboard
-	or mouse binding by calling 'ZoomIn' or 'ZoomOut'. Default is x2.
+	or mouse binding by calling 'ZoomIn' or 'ZoomOut'. Default is x2.0.
 
 *<magnifier><increment>*
 	Step by which magnification changes on each call to 'ZoomIn' or

docs/rc.xml.all

@@ -603,7 +603,7 @@
   <magnifier>
     <width>400</width>
     <height>400</height>
-    <initScale>2</initScale>
+    <initScale>2.0</initScale>
     <increment>0.2</increment>
     <useFilter>true</useFilter>
   </magnifier>

include/config/rcxml.h

@@ -144,7 +144,7 @@ struct rcxml {
 	/* Magnifier */
 	int mag_width;
 	int mag_height;
-	int mag_scale;
+	float mag_scale;
 	float mag_increment;
 	bool mag_filter;
 };

src/config/rcxml.c

@@ -1041,7 +1041,7 @@ entry(xmlNode *node, char *nodename, char *content)
 	} else if (!strcasecmp(nodename, "height.magnifier")) {
 		rc.mag_height = atoi(content);
 	} else if (!strcasecmp(nodename, "initScale.magnifier")) {
-		rc.mag_scale = atoi(content);
+		set_float(content, &rc.mag_scale);
 	} else if (!strcasecmp(nodename, "increment.magnifier")) {
 		set_float(content, &rc.mag_increment);
 	} else if (!strcasecmp(nodename, "useFilter.magnifier")) {
@@ -1255,7 +1255,7 @@ rcxml_init(void)
 
 	rc.mag_width = 400;
 	rc.mag_height = 400;
-	rc.mag_scale = 2;
+	rc.mag_scale = 2.0;
 	rc.mag_increment = 0.2;
 	rc.mag_filter = true;
 }

src/magnifier.c

@@ -60,6 +60,9 @@ magnify(struct output *output, struct wlr_buffer *output_buffer, struct wlr_box
 	if (mag_scale == 0.0) {
 		mag_scale = rc.mag_scale;
 	}
+	if (mag_scale == 0.0) {
+		mag_scale = 1.0;
+	}
 
 	if (fullscreen) {
 		width = output_buffer->width;