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## layout_painter

### Content

- Synopsis
- Keys, adding, getting and removing painters
- Table dimensions
- Cell access
- Measures
- Margin
- Merging cells

### Synopsis

The most powerful painter at the time is the layout_painter. You can compare layout_painter to a table (and indeed it is derived from class bg_wnd::table) and the cells are filled with other painters. layout_painter has the ability to store not only one painter but an unlimited number. Of course there are some table-specific functions like assigning painters to the cells, merging cells, sizing rows and columns, deleting them, ...

    namespace win32 { namespace gui {

         namespace bg_wnd {

              template <class CellData>
              class table
              {
              public:
                   // typedef's
                   typedef double factor;
                   typedef CellData cell_data;
                   typedef table<CellData> self;

                   typedef cell_proxy<self>                cell_type;
                   typedef const cell_proxy<const self>    const_cell_type;

                   // the big 4
                   table(const cell_data& def_cell_data)
                   table(const cell_data& def_cell_data, unsigned cols, unsigned rows);
                   table(const table& t);
                   virtual ~table()
                   const table& operator= (const table& t);

                   // cell access
                   const cell_data default_cell_data() const;
                   detail::forward_proxy<self> operator[] (unsigned col);
                   const detail::forward_proxy<const self> operator[] (unsigned col) const;

                   // row and column information
                   inline unsigned row_count() const;
                   unsigned col_count() const;
                   void row_height(unsigned row, factor height_factor);
                   factor row_height(unsigned row) const;
                   void col_width(unsigned col, factor width_factor);
                   factor col_width(unsigned col) const;

                   // row and column operations
                   void dimensions(unsigned cols, unsigned rows);
                   void insert_row(unsigned row);
                   void insert_col(unsigned col);
                   void remove_col(unsigned col);
                   void remove_row(unsigned row);

                   // merging
                   void merge_cells(const cell_range& range);
                   void unmerge_cells(const cell_range& range);
                   void unmerge_cells(COORDS coords);

                   void swap(self& t);
              };

         }    // namespace bg_wnd

         template <class Key = int>
         class layout_painter : public painter_base, public bg_wnd::table<Key>
         {
         public:
              // typedef's
              typedef Key key_type;
              typedef const key_type& param0;

              // exceptions
              typedef bg_wnd::general_exception<self, 0> key_already_used;
              typedef bg_wnd::general_exception<self, 1> key_invalid;
              typedef bg_wnd::general_exception<self, 2> invalid_painter_cast;

              // c'tor
              layout_painter(const key_type& empty_field) : Table(empty_field), horz_margin_(0), vert_margin_(0), bOuterMargin_(true)

              // virtual functions of painter_base
              layout_painter* clone() const;
              void draw(HDC hDC, int cx, int cy);

              // own functions
              void add_painter(const key_type& key, const painter_base& painter);
              template <class Painter> void add_painter(const key_type& key);
              template <class Painter> void add_painter(const key_type& key, typename Painter::param0 param);
              template <class Painter> void add_painter(const key_type& key, typename Painter::param0 param0, typename Painter::param1 param1);
              void delete_painter(const key_type& key);
              void delete_all_painters();
              std::vector<key_type> get_keys() const;
              template <class Painter> Painter& get_painter(const key_type& key) const;
              void margin(unsigned horz_margin, unsigned vert_margin, bool bOuterMargin = true);
              POINT margin() const;
         };

    } }  // namespace win32::gui

### Keys, adding, getting and removing painters

The usage of layout_painter is very similar to background_wnd_by_key. You have to specifiy a key type with which you can access the painters stored by layout_painter. Adding, getting and removing is identical to background_wnd_by_key - the functions are exactly the same (`add_painter()`, `get_painter` and `delete_painter()`). The only difference is that the exceptions thrown are of type `bg_wnd::general_exception<layout_painter<Key>, n>` (see here for further information about the exception system).
In the constructor you have to specify a default key. Cells are filled with this value by default. These cells are viewed as empty - they don't display any painter and so they are totally transparent.
Only add one painter once - it can be displayed multiple times. You can think of the key as an alias to a painter. First you add the painter with his key and then you connect the cells with this alias (see Cell access).

### Table dimensions

The next step that must be taken is to set the dimensions of the table. This can be done easily by calling the functions `dimensions()`, `insert_row()` and `insert_col()`. When you insert a row or column it is inserted before the passed row/column. To insert at the end pass a huge value to the function or use `dimensions()`.

### Cell access

When you have added all your painters and set up the dimensions you may wonder why nothing is displayed. As I mentioned before cells are filled by default with the empty key. You can fill them by setting the data of a cell to a key of an added painter. This allows more than one cell to be filled with one painter. Cell access is possible through `layout[0][0]`. The first index is the column, the second the row of the cell. Of course you are not allowed to use indices which are out of bound...(see Table dimensions).
What is returned by `operator[ ][ ]` is a `bg_wnd::cell_proxy<CellData>`-object which is typedefed to `cell_type` or `const_cell_type` in bg_wnd::table. The cell_proxy class gives you additional possibilities to retrieve information about the cell but the most important is surely to get and set the current data of a cell. To get the painter that is in a cell try this code:

    // assume layout is a layout_painter<std::string>...
    std::string key = layout[0][0];
    try {
         ipicture_painter& p = layout.get_painter<ipicture_painter> (key);
        ...   // do something with the painter
    }
    catch (l_painter::invalid_painter_cast&) {
         // painter is no ipicture_painter - get the painter_base
         painter_base& p = layout.get_painter (key);
         ...
    }
    catch (l_painter::key_invalid&) {
         // key is invalid (includes also default key passed to the c'tor)
         ...
    }

As you can see access to cells is very intuitive. One side note: cell (0, 0) is the upper left corner and (c - 1, r - 1) in a c x r table is on the lower right (this should be familiar to you).

Example:

    // typedef used in the following examples
    typedef layout_painter<std::string> l_painter;

    // create a layout_painter with the dimensions 3 x 3
    l_painter layout("empty");
    layout.dimensions(3, 3);

    // create painters and set the cells
    layout.add_painter<ipicture_painter> ("pic_beavis", "c:\\img1.jpg");
    layout.add_painter<tile_resource_painter> ("res", bg_wnd::res_info(IDI_BACKGROUND_WND, IMAGE_ICON));

    layout[0][0] = "res";
    layout[0][2] = "pic_beavis";
    layout[2][2] = "res";

    // add layout to the background_wnd and set a blue background_color
    add_painter(layout);
    bk_color(RGB(0, 0, 150));

The result is as follows

### Measures

Rows/columns and cells in a table only have logical measures or factors if you want. You have to provide a default width and height of a row and column and this value will be multiplied by the factor. layout_painter calculates the default values by dividing the dimensions of the drawing-rect through the count of rows/cols - this results in a constant arrangement of the cells and columns. If you want a column to be twice as big as the others, you have to call `col_height()`.
You can also get the logical position and height of a cell. Call cell_proxy's `log_left()`, `log_top()`, `log_width()` and `log_height()`. Merged cells are taken into account - if two horizontally adjacent cells are merged then `log_width()` would return 2.0 (assuming the column widths are 1.0).

Example:

    // create a layout_painter with the dimensions 3 x 2
    l_painter layout("empty");
    layout.dimensions(3, 2);

    // create painter and set the cells
    layout.add_painter<ipicture_painter> ("pic_beavis", "c:\\img1.jpg");

    // fill all cells
    for (unsigned col = 0; col < layout.col_count(); ++col)
         for (unsigned row = 0; row < layout.row_count(); ++row)
              layout[col][row] = "pic_beavis";

    // set width of first column to 1.5 as wide as the others
    layout.col_width(0, 1.5);

    l_painter::const_cell_type cell = layout[0][0];
    l_painter::factor f1 = cell.log_width();            // f1 = 1.5
    l_painter::factor f2 = cell.log_height();           // f2 = 1.0
    l_painter::factor f3 = cell.log_left();             // f3 = 0.0
    l_painter::factor f4 = layout[1][0].log_left();     // f4 = 1.5

    // add layout to the background_wnd
    add_painter(layout);

The result is as follows

### Margin

layout_painter has the ability to set a margin between cells. Just use `margin()`. The values passed are not logical - they are real pixels! There are two possibilities: with or without an additional border around the cells (that's the bOuterMargin argument).
Example:

    // create a layout_painter with the dimensions 3 x 2
    l_painter layout("empty");
    layout.dimensions(3, 2);

    // create painter and set the cells
    layout.add_painter<ipicture_painter> ("pic_beavis", "c:\\img1.jpg");
    for (unsigned col = 0; col < layout.col_count(); ++col)
         for (unsigned row = 0; row < layout.row_count(); ++row)
              layout[col][row] = "pic_beavis";

    // set the margin
    bool bOuterMargin = ...;
    layout.margin(20, 10, bOuterMargin);

    // add layout to the background_wnd and set a blue background_color
    add_painter(layout);
    bk_color(RGB(0, 0, 150));

The result is as follows

bOuterMargin = true | bOuterMargin = false

### Merging cells

Merging cells is achieved through `merge_cells()`. It takes a bg_wnd::cell_range-object as a parameter which identifies the range of the cells to merge. If this range intersects an existing range of merged cells, they are combined to one large range.
When you insert or delete a row or column where there are merged cells the behaviour is the same as in Excel.
You can unmerge cells with `unmerge_cells()`. When unmerging cells the painters which were assigned to these cells before merging are restored.
To get the range of a cell you can call cell_proxy's `range()`-function. When a cell is in a merged range the whole range is returned.
Note: When you merge cells only the painter in the upper left corner is drawn for the whole range. If the upper left cell was empty then nothing is displayed!
Example:

    // create a layout_painter with the dimensions 3 x 2
    l_painter layout("empty");
    layout.dimensions(3, 2);

    // create painters and set the cells
    layout.add_painter<ipicture_painter> ("pic_beavis", "c:\\img1.jpg");

    // fill all cells
    for (unsigned col = 0; col < layout.col_count(); ++col)
         for (unsigned row = 0; row < layout.row_count(); ++row)
              layout[col][row] = "pic_beavis";

    // merge the cells
    layout.merge_cells( bg_wnd::cell_range(bg_wnd::COORDS(0, 0), 1, 2) );

    bg_wnd::cell_range range = layout[0][0].range();  // range = (0, 0) - (0, 1)

    // add layout to the background_wnd
    add_painter(layout);

The result is as follows

| by Steven Weiss. You can contact me at steven11@gmx.de.