geom: supplement :combine with more generic .boundingBox

It is a bit cleaner to do all of the necessary looping over lists of
Geoms within a straight-forward Geom.boundingBox function rather than
looping over :combine every time (or reimplementing :combine in some
cases). Geom:combine can be trivially reimplemented in terms of
Geom.boundingBox as well.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

frontend/document/credocument.lua

@@ -561,25 +561,14 @@ function CreDocument:getWordFromPosition(pos)
         if text_range.pos0 and text_range.pos1 then
             -- get segments from these pos, to build the overall box
             local word_boxes = self._document:getWordBoxesFromPositions(text_range.pos0, text_range.pos1, true)
-            if #word_boxes > 0 then
-                local overall_box
-                for i = 1, #word_boxes do
-                    local line_box = word_boxes[i]
-                    if not overall_box then
-                        overall_box = line_box
-                    else
-                        if line_box.x0 < overall_box.x0 then overall_box.x0 = line_box.x0 end
-                        if line_box.y0 < overall_box.y0 then overall_box.y0 = line_box.y0 end
-                        if line_box.x1 > overall_box.x1 then overall_box.x1 = line_box.x1 end
-                        if line_box.y1 > overall_box.y1 then overall_box.y1 = line_box.y1 end
-                    end
-                end
-                wordbox.sbox = Geom:new{
-                    x = overall_box.x0,
-                    y = overall_box.y0,
-                    w = overall_box.x1 - overall_box.x0,
-                    h = overall_box.y1 - overall_box.y0,
-                }
+            -- convert to Geom so we can use Geom.boundingBox
+            for i=1, #word_boxes do
+                local v = word_boxes[i]
+                word_boxes[i] = { x = v.x0,        y = v.y0,
+                                  w = v.x1 - v.x0, h = v.y1 - v.y0 }
+            end
+            wordbox.sbox = Geom.boundingBox(word_boxes)
+            if wordbox.sbox then
                 box_found = true
             end
         end

frontend/document/koptinterface.lua

@@ -789,14 +789,7 @@ function KoptInterface:getClipPageContext(doc, pos0, pos1, pboxes, drawer)
     assert(pos0.zoom == pos1.zoom)
     local rect
     if pboxes and #pboxes > 0 then
-        local box = pboxes[1]
-        rect = Geom:new{
-            x = box.x, y = box.y,
-            w = box.w, h = box.h,
-        }
-        for _, _box in ipairs(pboxes) do
-            rect = rect:combine(Geom:new(_box))
-        end
+        rect = Geom.boundingBox(pboxes)
     else
         local zoom = pos0.zoom or 1
         rect = {
@@ -1241,14 +1234,9 @@ function KoptInterface:nativeToPageRectTransform(doc, pageno, rect)
             y = rect.y + rect.h - 5
         }
         local boxes = self:getPageBoxesFromPositions(doc, pageno, pos0, pos1)
-        local res_rect = nil
-        if #boxes > 0 then
-            res_rect = boxes[1]
-            for _, box in pairs(boxes) do
-                res_rect = res_rect:combine(box)
-            end
+        if boxes then
+            return Geom.boundingBox(boxes)
         end
-        return res_rect
     else
         return rect
     end

frontend/ui/geometry.lua

@@ -144,27 +144,7 @@ Works for rectangles, dimensions and points
 @treturn Geom
 ]]
 function Geom:combine(rect_b)
-    -- We'll want to return a *new* object, so, start with a copy of self
-    local combined = self:copy()
-    if not rect_b or rect_b:area() == 0 then return combined end
-
-    if combined.x > rect_b.x then
-        combined.x = rect_b.x
-    end
-    if combined.y > rect_b.y then
-        combined.y = rect_b.y
-    end
-    if self.x + self.w > rect_b.x + rect_b.w then
-        combined.w = self.x + self.w - combined.x
-    else
-        combined.w = rect_b.x + rect_b.w - combined.x
-    end
-    if self.y + self.h > rect_b.y + rect_b.h then
-        combined.h = self.y + self.h - combined.y
-    else
-        combined.h = rect_b.y + rect_b.h - combined.y
-    end
-    return combined
+    return Geom.boundingBox({self, rect_b})
 end
 
 --[[--
@@ -439,4 +419,34 @@ function Geom:isEmpty()
     return false
 end
 
+--[[--
+Returns a bounding box which encompasses all passed rectangles.
+@tparam Geom rectangles to encompass
+@treturn Geom bounding box or nil if no rectangles passed
+]]
+function Geom.boundingBox(boxes)
+    local bounding_box
+    for _, geom in ipairs(boxes) do
+        -- Easier to work with (x0,x0)+(x1,y1) pairs.
+        local box = { x0 = geom.x, y0 = geom.y,
+                      x1 = geom.x + geom.w, y1 = geom.y + geom.h }
+        if not bounding_box then
+            bounding_box = box
+        else
+            if box.x0 < bounding_box.x0 then bounding_box.x0 = box.x0 end
+            if box.y0 < bounding_box.y0 then bounding_box.y0 = box.y0 end
+            if box.x1 > bounding_box.x1 then bounding_box.x1 = box.x1 end
+            if box.y1 > bounding_box.y1 then bounding_box.y1 = box.y1 end
+        end
+    end
+    if bounding_box then
+        return Geom:new{
+            x = bounding_box.x0,
+            y = bounding_box.y0,
+            w = bounding_box.x1 - bounding_box.x0,
+            h = bounding_box.y1 - bounding_box.y0,
+        }
+    end
+end
+
 return Geom