ENH: Adding Draw Example for Display Area

leafyrabbet · leafyrabbet · commit c14911d591a1 · 2020-05-23T16:42:28.000-04:00
- `cairomm` library added to support vector graphics
- Makefile (macOS) updated to support `cairomm`
- Callback/Handler function updated for drawing
- Example line drawing used from GNOME documentation
- BRK: This will break SemaphoreCI due to missing libs for build environment
diff --git a/calculator_simple/build/macos/Makefile b/calculator_simple/build/macos/Makefile
@@ -36,7 +36,8 @@ COMPILER_WITH_FLAGS := $(COMPILER) $(FLAGS)
 
 LIB_GTKMM = gtkmm-3.0
 LIB_GLIB = glib-2.0
-PKG_CONFIG_LIBS := $(LIB_GTKMM) $(LIB_GLIB)
+LIB_CAIRO = cairomm-1.0
+PKG_CONFIG_LIBS := $(LIB_GTKMM) $(LIB_GLIB) $(LIB_CAIRO)
 OTHER_LIBS := -lstdc++
 LIBS := $(OTHER_LIBS) `pkg-config --cflags --libs $(PKG_CONFIG_LIBS)`
 
diff --git a/calculator_simple/src/app_window.cpp b/calculator_simple/src/app_window.cpp
@@ -140,6 +140,9 @@ AppWindow::AppWindow():
    layout_buttons.attach(btn_alt_dot_obj, 1, 4, 1, 1);
    layout_buttons.attach(btn_alt_inv_obj, 4, 4, 1, 1);
 
+
+   display_area.signal_draw().connect(sigc::mem_fun(*this, &AppWindow::handle_display_update), false);
+
    layout_display.pack_start(display_area);
 
    layout_main.pack_start(layout_display);
@@ -163,9 +166,34 @@ AppWindow::~AppWindow()
 /**
  * @brief   Handler method for the display area redraws.
  */
-void AppWindow::handle_display_update()
+bool AppWindow::handle_display_update(
+   ::Cairo::RefPtr<::Cairo::Context> const & draw_context_ptr
+)
 {
-   return;
+   display_area_allocation = display_area.get_allocation();
+   int const area_x_full = display_area_allocation.get_width();
+   int const area_y_full = display_area_allocation.get_height();
+
+   int const top_left_x = (0);
+   int const top_left_y = (0);
+
+   int const center_x = (area_x_full / 2);
+   int const center_y = (area_y_full / 2);
+
+   int const bot_rght_x = (area_x_full);
+   int const bot_rght_y = (area_y_full);
+
+
+   draw_context_ptr->set_line_width(10.0);
+   draw_context_ptr->set_source_rgb(0.8, 0.0, 0.0);
+   draw_context_ptr->move_to(top_left_x, top_left_y);
+   draw_context_ptr->line_to(center_x, center_y);
+   draw_context_ptr->line_to(top_left_x, bot_rght_y);
+   draw_context_ptr->move_to(center_x, center_y);
+   draw_context_ptr->line_to(bot_rght_x, center_y);
+   draw_context_ptr->stroke();
+
+   return PROPAGATE_SIG; // Should propagate to make sure save/restore are processed correctly.
 }
 
 
diff --git a/calculator_simple/src/app_window.hpp b/calculator_simple/src/app_window.hpp
@@ -23,6 +23,8 @@
 #include <gtkmm/scale.h>
 #include <gtkmm/button.h>
 
+#include <cairomm/context.h>
+
 #include <array>
 
 #include "logic_calculator.hpp"
@@ -36,7 +38,9 @@ class AppWindow :
       virtual ~AppWindow();
  
    protected:
-      void handle_display_update();
+      bool handle_display_update(
+            ::Cairo::RefPtr<::Cairo::Context> const & draw_context_ptr
+      );
       
       bool handle_radix_change(
               Gtk::ScrollType const & scroll_type
@@ -70,6 +74,7 @@ class AppWindow :
       Gtk::Grid layout_buttons;
 
       Gtk::DrawingArea display_area;
+      Gtk::Allocation display_area_allocation;
 
       Gtk::Label radix_label_obj;
       Gtk::Scale radix_slider_obj;
