Don't restrict page sizes unnecessarily.

Also don't validate custom sizes unless they are enabled.

Fixes https://gitlab.com/kicad/code/kicad/issues/8880

common/dialogs/dialog_page_settings.cpp

@@ -202,11 +202,17 @@ bool DIALOG_PAGES_SETTINGS::TransferDataToWindow()
 
 bool DIALOG_PAGES_SETTINGS::TransferDataFromWindow()
 {
-    if( !m_customSizeX.Validate( MIN_PAGE_SIZE_MILS, m_maxPageSizeMils.x, EDA_UNITS::MILS ) )
-        return false;
+    int idx = std::max( m_paperSizeComboBox->GetSelection(), 0 );
+    const wxString paperType = m_pageFmt[idx];
+
+    if( paperType.Contains( PAGE_INFO::Custom ) )
+    {
+        if( !m_customSizeX.Validate( MIN_PAGE_SIZE_MILS, m_maxPageSizeMils.x, EDA_UNITS::MILS ) )
+            return false;
 
-    if( !m_customSizeY.Validate( MIN_PAGE_SIZE_MILS, m_maxPageSizeMils.y, EDA_UNITS::MILS ) )
-        return false;
+        if( !m_customSizeY.Validate( MIN_PAGE_SIZE_MILS, m_maxPageSizeMils.y, EDA_UNITS::MILS ) )
+            return false;
+    }
 
     if( SavePageSettings() )
     {

include/page_info.h

@@ -36,7 +36,7 @@
 #include <base_units.h>     // for IU_PER_MILS
 
 /// Min and max page sizes for clamping, in mils.
-#define MIN_PAGE_SIZE_MILS          4000
+#define MIN_PAGE_SIZE_MILS           100
 #define MAX_PAGE_SIZE_PCBNEW_MILS  48000
 #define MAX_PAGE_SIZE_MILS        120000