grid: Set grid to use integer pixels

Each dot is an integer number of pixels wide, so supporting 0.5 width
steps no longer makes sense.  We round up the existing settings to the
nearest integer and only allow integers in the dialog.

Fixes: lp:1816748
* https://bugs.launchpad.net/kicad/+bug/1816748

common/gal/gal_display_options.cpp

@@ -51,7 +51,7 @@ GAL_DISPLAY_OPTIONS::GAL_DISPLAY_OPTIONS()
     : gl_antialiasing_mode( OPENGL_ANTIALIASING_MODE::NONE ),
       cairo_antialiasing_mode( CAIRO_ANTIALIASING_MODE::NONE ),
       m_gridStyle( GRID_STYLE::DOTS ),
-      m_gridLineWidth( 0.5 ),
+      m_gridLineWidth( 1.0 ),
       m_gridMinSpacing( 10.0 ),
       m_axesEnabled( false ),
       m_fullscreenCursor( false ),
@@ -67,7 +67,7 @@ void GAL_DISPLAY_OPTIONS::ReadConfig( wxConfigBase* aCfg, const wxString& aBaseN
                 static_cast<long>( KIGFX::GRID_STYLE::DOTS ) );
     m_gridStyle = UTIL::GetValFromConfig( gridStyleConfigVals, readLong );
 
-    aCfg->Read( aBaseName + GalGridLineWidthConfig, &m_gridLineWidth, 0.5 );
+    aCfg->Read( aBaseName + GalGridLineWidthConfig, &m_gridLineWidth, 1.0 );
     aCfg->Read( aBaseName + GalGridMaxDensityConfig, &m_gridMinSpacing, 10 );
     aCfg->Read( aBaseName + GalGridAxesEnabledConfig, &m_axesEnabled, false );
     aCfg->Read( aBaseName + GalFullscreenCursorConfig, &m_fullscreenCursor, false );

common/gal/graphics_abstraction_layer.cpp

@@ -108,7 +108,7 @@ bool GAL::updatedGalDisplayOptions( const GAL_DISPLAY_OPTIONS& aOptions )
 
     if( options.m_gridLineWidth != gridLineWidth )
     {
-        gridLineWidth = options.m_gridLineWidth ;
+        gridLineWidth = std::floor( options.m_gridLineWidth + 0.5 );
         refresh = true;
     }
 

common/widgets/gal_options_panel.cpp

@@ -32,9 +32,9 @@
 /*
  * Spin control parameters
  */
-static const double gridThicknessMin = 0.5;
+static const double gridThicknessMin = 1.0;
 static const double gridThicknessMax = 10.0;
-static const double gridThicknessStep = 0.5;
+static const double gridThicknessStep = 1.0;
 
 static const double gridMinSpacingMin = 5;
 static const double gridMinSpacingMax = 200;
@@ -134,7 +134,7 @@ GAL_OPTIONS_PANEL::GAL_OPTIONS_PANEL( wxWindow* aParent, KIGFX::GAL_DISPLAY_OPTI
 
         m_gridSizeIncrementer->SetStep( gridThicknessMin, gridThicknessMax,
                                         gridThicknessStep );
-        m_gridSizeIncrementer->SetPrecision( 1 );
+        m_gridSizeIncrementer->SetPrecision( 0 );
 
         m_gridMinSpacingIncrementer = std::make_unique<SPIN_INCREMENTAL_TEXT_CTRL>(
                     *m_gridMinSpacingSpinBtn, *m_gridMinSpacing );
@@ -214,7 +214,7 @@ bool GAL_OPTIONS_PANEL::TransferDataFromWindow()
     m_galOptions.m_gridStyle = UTIL::GetValFromConfig(
             gridStyleSelectMap, m_gridStyle->GetSelection() );
 
-    m_galOptions.m_gridLineWidth = m_gridSizeIncrementer->GetValue();
+    m_galOptions.m_gridLineWidth = std::floor( m_gridSizeIncrementer->GetValue() + 0.5 );
 
     m_galOptions.m_gridMinSpacing = m_gridMinSpacingIncrementer->GetValue();