Bug 1484125 - part 1: Create TableSize struct to compute and store nu…

…mber of rows and columns of a <table> element r=m_kato

HTMLEditor::GetTableSize() is an XPCOM method but used internally a lot.
Therefore, it shouldn't be called for internal use.  Additionally, the
callers need to declare two int32_t variables, but this causes the code
messy.  Therefore, this patch creates TableSize struct and it implements
HTMLEditor::GetTableSize().  Then, all callers of it is replaced with
TableSize struct.

New TableSize struct does not support computes <table> element from anchor
of Selection since there is no user of this in C++ code.

Differential Revision: https://phabricator.services.mozilla.com/D3953

--HG--
extra : moz-landing-system : lando

editor/libeditor/HTMLEditor.h

@@ -1065,6 +1065,45 @@ class HTMLEditor final : public TextEditor
                 ErrorResult& aRv);
   };
 
+  /**
+   * TableSize stores and computes number of rows and columns of a <table>
+   * element.
+   */
+  struct MOZ_STACK_CLASS TableSize final
+  {
+    int32_t mRowCount;
+    int32_t mColumnCount;
+
+    /**
+     * @param aHTMLEditor               The editor which creates the instance.
+     * @param aTableOrElementInTable    If a <table> element, computes number
+     *                                  of rows and columns of it.
+     *                                  If another element in a <table> element,
+     *                                  computes number of rows and columns
+     *                                  of nearest ancestor <table> element.
+     *                                  Otherwise, i.e., non-<table> element
+     *                                  not in <table>, returns error.
+     * @param aRv                       Returns error if the element is not
+     *                                  in <table> or layout information is
+     *                                  not available.
+     */
+    TableSize(HTMLEditor& aHTMLEditor, Element& aTableOrElementInTable,
+              ErrorResult& aRv)
+      : mRowCount(-1)
+      , mColumnCount(-1)
+    {
+      MOZ_ASSERT(!aRv.Failed());
+      Update(aHTMLEditor, aTableOrElementInTable, aRv);
+    }
+
+    /**
+     * Update mRowCount and mColumnCount for aTableOrElementInTable.
+     * See above for the detail.
+     */
+    void Update(HTMLEditor& aHTMLEditor, Element& aTableOrElementInTable,
+                ErrorResult& aRv);
+  };
+
   /**
    * PasteInternal() pasts text with replacing selected content.
    * This tries to dispatch ePaste event first.  If its defaultPrevent() is